# Copyright and license of Julia packages

**URL:** <https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598>\
**Category:** General Usage\
**Tags:** question\
**Created:** [June 3, 2025, 2:10pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598 "2025-06-03T14:10:09Z")\
**Posts on this page:** 18\
**Page:** 2

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**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [June 3, 2025, 6:04pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/22 "2025-06-03T18:04:39Z")

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> [@goerz](#):
>
> I would limit it to a single line, certainly not the whole multi-paragraph license notice.

Well, I use two lines now:

```julia
# Copyright (c) 2020, 2021, 2022, 2024 Uwe Fechner and Bart van de Lint
# SPDX-License-Identifier: MIT

```

Lets see if our data steward is happy with it.

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**Author:** ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)\
**Post date:** [June 3, 2025, 7:25pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/23 "2025-06-03T19:25:05Z")

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> [@goerz](#):
>
> I lack the imagination to see how files get separated from their repo in any realistic scenario of an open-source Julia project.

Sometimes it is tempting to copy a file rather than adding a dependency, especially in ecosystems lacking convenient package managers — for example, JuliaLang/julia itself contains several C files that were copied from other projects (with copyright headers).

Julia’s package manager reduces the temptation to copy code from other projects, but I’m sure it still happens from time to time when people don’t want to add a dependency for one little thing. And it is even more likely in cases where you want code from a project that is defunct and unmaintained. Hopefully people are careful to attribute such code and copy the license info, but historically many software developers are unsophisticated about copyright.

Adding a header to each file makes it a bit less likely to lose copyright info in such scenarios. Unfortunately, I suspect it’s less effective in a language like Julia where “file scope” is not significant. If people just copy snippets of a file, they are more likely to lose a copyright header.

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**Author:** ![tecosaur](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tecosaur/32/23206_2.png) [@tecosaur](https://discourse.julialang.org/u/tecosaur)\
**Post date:** [June 3, 2025, 7:27pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/24 "2025-06-03T19:27:16Z")

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As part of my previous thinking around copyright, I came around to the value of per-file “hey, I’m part of a project using license X” statements, as promoted by efforts like [https://reuse.software](https://reuse.software).

The main reason against it IMO is the hassle, so I once again ignored [xkcd: Is It Worth the Time?](https://xkcd.com/1205) and wrote [tec/headlice: Automatic license headers, and other licensing utilities - Code by TEC](https://code.tecosaur.net/tec/headlice), which entirely handles it in the background.

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [June 4, 2025, 1:07am UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/25 "2025-06-04T01:07:16Z")

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Google has a suggested header for source files: [Non-Apache License Text Headers &nbsp;|&nbsp; Google Open Source](https://opensource.google/documentation/reference/releasing/licenses)

We do this for all packages in `jump-dev`:

> <https://github.com/jump-dev/MathOptInterface.jl/blob/9aba539f227f22c90b66a9c1d476d46c56acb78f/src/MathOptInterface.jl#L1-L5>

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<div class="post-metadata">

**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [June 4, 2025, 10:07am UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/26 "2025-06-04T10:07:25Z")

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The university wants us to use this tool: [Tutorial: How to become REUSE-compliant | REUSE](https://reuse.software/tutorial/)

I am not so happy about it, because it means we have to attach a license to each and every file, even Project.toml or `.gitignore`. But I just did it for my main project, KiteModels.jl, I hope they are happy now.

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**Author:** ![StefanKarpinski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stefankarpinski/32/24_2.png) [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)\
**Post date:** [June 4, 2025, 12:55pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/27 "2025-06-04T12:55:03Z")

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Julia itself uses a one-line license header:

```julia
# This file is a part of Julia. License is MIT: https://julialang.org/license

```

Having a ton of boilerplate in each file seems very excessive, so we went for the smallest header we could and use a link that redirects to the actual license file (in case it moves).

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**Author:** ![goerz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/goerz/32/3269_2.png) [@goerz](https://discourse.julialang.org/u/goerz)\
**Post date:** [June 4, 2025, 3:04pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/28 "2025-06-04T15:04:48Z")

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> [@ufechner7](#):
>
> The university wants us to use this tool: [Tutorial: How to become REUSE-compliant | REUSE](https://reuse.software/tutorial/)

So, presumably, that tells you exactly how they measure compliance: you have to make `reuse lint` pass. That gives you a chance to keep things sane while fulfilling the requirements.

Those REUSE tags don’t seem to be terrible (two comment lines per file). I very much liked the blog post [How and why to properly write copyright statements in your code - … and probably more than what you ever wanted to know about them · Hook’s Humble Homepage](https://matija.suklje.name/how-and-why-to-properly-write-copyright-statements-in-your-code) linked in the README of [@tecosaur’s tool](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/24). That really addresses a lot of my concerns, and gives clear information about details I would have been quite unclear on, like whether you need to bump the year every January 1st (you do not).

> [@ufechner7](#):
>
> I am not so happy about it, because it means we have to attach a license to each and every file, even Project.toml or `.gitignore`

The idea that a `.gitignore` file is copyrightable at all is pretty bizarre. In any case, though, I would probably cover these files with a [`REUSE.toml` file](https://reuse.software/faq/#bulk-license). That seems like a much cleaner option than adding a bunch of files like `.gitignore.license` files to your repo. And the TOML format seems like it allows you to define meaningful wildcards to keep the overhead pretty manageable. I think it would be pretty easy to add the two-line SPDX header to every actual source code file, cover the rest of the files via a `REUSE.toml` file, and thus make the `reuse lint` tool happy, and your university’s compliance officer, by extension.

As for the general point:

> [@stevengj](#):
>
> Sometimes it is tempting to copy a file rather than adding a dependency,

To be clear, I do that all the time. And then, yes, I usually add comments to point back to the original project, even on a function-level like in

> <https://github.com/JuliaQuantumControl/GRAPE.jl/blob/09973b88a9d941fc26d66fda40a502d163b82f83/src/workspace.jl#L454-L455>

I might start using the [SPDX snippet syntax](https://reuse.software/faq/#partial-license) for that. It seems like a very thought-out and standardized system.

> [@stevengj](#):
>
> Adding a header to each file makes it a bit less likely to lose copyright info in such scenarios.

I suppose that’s true. My point was that I never had any trouble identifying the original license when I vendored third-party code. Referencing the original license information is on me, in any case, but I can’t argue with the idea that the original files all containing minimal license headers makes it more likely that the information isn’t lost accidentally.

The minimal SPDX headers seem pretty reasonable to this end, and the only real concern would be the overhead of adding them, i.e., the requirement to set up some tooling. I don’t think it’s a bad idea, if someone wants to do it, and [https://reuse.software](https://reuse.software) provides all the building blocks. Putting a multi-paragraph license text at the top of each file, as the GPL asks for, is still something I would consider absurd in today’s world.

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<div class="post-metadata">

**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [June 19, 2025, 2:21pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/29 "2025-06-19T14:21:13Z")

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I can think of three scenarios where licenses matter:

1. **Users** You want to make the life of well-meaning users easier, because unless your code has a license, they cannot (legally) use it. In this case, single `LICENSE.md` in the root should be sufficient.

2. **Protection** You want to protect your rights. In this case I understand the _theoretical_ argument of having a statement in each file, but _in practice_, given that most Julia packages have a permissive, MIT-like license, why would anyone steal your code? Copying code from a package is absolutely unnecessary and at the same time the perfect footgun, because you will miss out on unit tests, bug fixes, updates, etc. It is really a crime with a built-in punishment. And let’s be frank, if politely asking someone to remove your copyrighted code they used in a way not permitted by the license doesn’t work, are you willing to go to court, possibly in another country? Really?

3. **Compliance** This case is simple, because unless you want to fight the system, you will have to do as they say.

This topic is confusing because it is really about (3), but that was not clear from the start, so (1) and (2) are mixed in. But in this context they are not relevant.

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**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [June 19, 2025, 4:16pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/30 "2025-06-19T16:16:42Z")

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While all you say is true, I found it helpful to have these per file copyrights. For example, I found out that the copyright for one 3D CAD file that I use is with my prof. So whoever wants to reuse this file should ask my prof and not me (well, or not ask him, but at least give reference to him as author). And one of my students prefers the MPL-2.0 to the MIT license. Not sure if you can easily mix different licenses in one Julia package, but these licenses are compatible so we just use both in the package.

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**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [June 19, 2025, 4:49pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/31 "2025-06-19T16:49:57Z")

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I think that the right level of granularity for licensing Julia code in packages is… _packages_ 😉 Preferably all code in the package should have the same license (may be multiple compatible licenses if preferred, but they should really apply to all code).

Otherwise, you are setting yourself up for a nightmare, eg if you refactor and move code between files (which happens frequently), do you keep track of each snippet?

If package authors cannot agree on a single license, they should consider packaging the code separately. Julia makes it easy (an, in some cases, preferable) to have small, focused packages.

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**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [June 19, 2025, 4:52pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/32 "2025-06-19T16:52:24Z")

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Well, we have multiple models in one package, and I will not change that unless I have to, I am already in charge of 10 packages and do not want to increase the number unless really needed.  
And the different models are in different files and have different authors, so I do not see a problem to have two different licenses for the different models.

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**Author:** ![goerz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/goerz/32/3269_2.png) [@goerz](https://discourse.julialang.org/u/goerz)\
**Post date:** [June 19, 2025, 5:13pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/33 "2025-06-19T17:13:13Z")

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This thread has actually changed my opinion somewhat, and I’m strongly considering adopting [https://reuse.software/](https://reuse.software/) even outside of any formal compliance requirements in my organization. The per-file copyright management seems like a good idea. I want my _code_ to be MIT licensed. But code licenses aren’t actually appropriate for non-code material (and vice versa). So I would in fact want the `.md` files, or images in the documentation to be licensed under `CC BY-SA` (or maybe `CC BY`, haven’t made up my mind yet), and “infrastructure files” such as a `Makefile`, build scripts, etc. should probably be in the public domain (`CC0`).

What was holding me back was lack of tooling to manage all that, but REUSE provides exactly that in what seems to be a well-thought-out system.

I agree though that intermixing multiple code licenses like MIT and MPL seems like a bad idea.

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**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [June 19, 2025, 5:51pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/34 "2025-06-19T17:51:43Z")

</div>

What I don’t understand is the legal basis for `SPDX-FileCopyrightText:` being a copyright notice. I understand that they have an ISO standard, but that does not make it law. AFAIK the law requires “Copyright” or “©”.

Frankly, I also don’t see the use case for REUSE from a FOSS developer perspective. I fully understand that it makes compliance people happy, because they can now _Audit_ something with a tool and little green checkmarks come up if it is OK, and now they can say that they have _Audited The Project_ with a _Dedicated Tool_, and _All Is In Order and Everything is Compliant_, etc.

**But that information was already in the `LICENSE` file.** This just adds red tape to the process for no clear reason. As long as it is optional, that is fine with me, but I am concerned that it will be come a requirement by habit.

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**Author:** ![goerz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/goerz/32/3269_2.png) [@goerz](https://discourse.julialang.org/u/goerz)\
**Post date:** [June 19, 2025, 7:07pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/35 "2025-06-19T19:07:29Z")

</div>

> [@Tamas\_Papp](#):
>
> AFAIK the law requires “Copyright” or “©”.

This is answered in [How and why to properly write copyright statements in your code - … and probably more than what you ever wanted to know about them · Hook’s Humble Homepage](https://matija.suklje.name/how-and-why-to-properly-write-copyright-statements-in-your-code#why-the-sign) as well as in the [REUSE FAQ](https://reuse.software/faq/#copyright-symbol). In short, it’s a good idea to add `©`, including in the `SPDX-FileCopyrightText`, but it doesn’t make the copyright any more or less valid, since copyright is automatic (at least since 1989).

> But that information was already in the `LICENSE` file.

If the LICENSE file can cover all files in the repo (which [REUSE argues it cannot](https://reuse.software/faq/#why-care)), then yes.

> little green checkmarks come up if it is OK

I gotta admit I’m a sucker for little green checkmarks myself 😉

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**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [June 19, 2025, 7:27pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/36 "2025-06-19T19:27:44Z")

</div>

> [@goerz](#):
>
> If the LICENSE file can cover all files in the repo (which [REUSE argues it cannot](https://reuse.software/faq/#why-care)), then yes.

I have read that multiple times and I don’t find the argument convincing. Actually, I am having a hard time even reconstructing an argument, they just keep repeating that they think every file should have a license statement, but it is unclear why.

Just to be specific, I think that the widespread convention that the nearest `LICENSE` file you find by going through parent directories is the effective one works just fine. You can do

```julia
LICENSE
Project.toml
src/
    PackageName.jl
test/
docs/
    src/
        LICENSE

```

where `/docs/src/LICENSE` is your preferred license for your documentation, but everything else is licensed under `/LICENSE`.

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**Author:** ![goerz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/goerz/32/3269_2.png) [@goerz](https://discourse.julialang.org/u/goerz)\
**Post date:** [June 19, 2025, 7:46pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/37 "2025-06-19T19:46:02Z")

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Yeah, I probably agree with you (and I would _definitely_ have agreed with you at the start of this thread).

I suppose they have some notion of standardization / machine readability / making sure that _every_ file is _unambiguously_ licensed, plus the assumption that complex projects will need to include files with different licenses. That’s debatable at best, and probably massive overkill. I would not want to insist that people must adopt REUSE unless they’re being forced to by some compliance officer at their organization, or unless they have a warped sense of this kind of thing being “fun” (which might be a category I put myself in).

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**Author:** ![gwr](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gwr/32/33632_2.png) [@gwr](https://discourse.julialang.org/u/gwr)\
**Post date:** [July 17, 2025, 5:45pm UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/38 "2025-07-17T17:45:25Z")

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Great topic and I just recently had that discussion in the Modelica community, which complicates things as tools serialize the code, so that code may end up in more or less files than you had intended (see [here](https://github.com/modelica/ModelicaSpecification/issues/3680)).

My last post there kind of wraps things up and most of it should carry over to this community as well.

[https://github.com/modelica/ModelicaSpecification/issues/3680#issuecomment-2866339224](https://github.com/modelica/ModelicaSpecification/issues/3680#issuecomment-2866339224)

Some key points:

1. **Your copyright needs no explicit statement, but …** You do have a copyright the moment you _create_ something, which is not trivial (to give a loose definition). Including per file headers is a **precaution** that you (or your organization) may take or not. The advantage is that it is ultimately extremely safe as it is _machine_ **and** _human_ readable at the raw source level.

2. **REUSE compliance is much less hassle than it looks.** As has been pointed out here before, you can use a `REUSE.toml` to elegantly assign SPDX headers to multiple files _en bloc_. This extremely lightens the burden of adding labels to files like `.gitignore` or tons of image files. Finally, there are _pre-commit hooks_ to add SPDX tags conveniently to files still lacking one.

3. **A single license file does not meet today’s complexity.** With just two lines of SPDX tags a lot of ambiguity can be removed. Why shouldn’t some of the _images_ that I ship in my project have a different license than the stricter one given for the main code? (It’s also extremely likely that those artifacts get distributed separately down the road.) It’s also a good idea to explicitly separate branding and trademark related copyrights from the rest. Often the license text does address this (but not always), yet the license file in my repo and the file with my corporate logo may get separated. I find it nice that there is an additional way to explicitly label that logo a “proprietary asset” even in an open source project.

#### TL;DR

In Julia, we value the flexibility and composability of _multiple dispatch_. It’s interesting to see, how the very same people that value this kind of flexibility still believe a single license file in a repo is all that should ever be needed in a _world of composition (e.g., copy & paste)_. 🙂  
The legal world of IP is surprisingly more complicated than it may look. The REUSE specification imho goes a long way in dealing with that complexity in a rather clear, unambiguous, and even convenient way.

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<div class="post-metadata">

**Author:** ![tecosaur](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tecosaur/32/23206_2.png) [@tecosaur](https://discourse.julialang.org/u/tecosaur)\
**Post date:** [July 18, 2025, 3:04am UTC](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598/39 "2025-07-18T03:04:54Z")

</div>

> [@gwr](#):
>
> Great topic and I just recently had that discussion in the Modelica community

Since you found this discussion interesting, I think it’s probably worth mentioning an earlier discussion that overlaps a bit with this one that you might also find to be of interest 🙂

> [@Package licenses: Contemplations and considerations](https://discourse.julialang.org/t/package-licenses-contemplations-and-considerations/117922):
>
> I’ve recently been giving more thoughts to the way I license my packages. While I don’t anticipate the choice becoming practically significant any times soon, I’ve realised that the topic probably deserves more consideration that I’ve previously given it. Why we need to think about licenses While many of us want to “just do (F)OSS” without paying much attention to licenses, they are an unavoidable part of the landscape due to the way intellectual property law has developed over the last several…

[Previous page](https://discourse.julialang.org/t/copyright-and-license-of-julia-packages/129598.md?page=1)