Can you explain a bit about how these packages would be used? Would the Python packages that depend on them do a juliacall type thing to import them?
I feel like CamelCase is part of the identity of Julia packages, so I hope the capitalization turns out to be okay in the end. But if it isn’t, the julia- name seems fine, with the CamelCase becoming snake_case - for ApproxFun.jl becoming julia-approx_fun (assuming underscores are allowed).
The julia- prefix does seem a bit long, especially with names like SplitApplyCombine.jl - it becomes the even longer julia-split_apply_combine. But (slightly) shortening it to split_apply_combine-jl or jl-split_apply_combine doesn’t sound as nice. However, the shortened names do have the benefit that they emphasize the name of the package itself more.
I like that split_apply_combine-jl sounds pretty close to the package’s original name, but I also like the explicitness of julia-split_apply_combine. Knowing some of the context of where and how it will be used will help decide which one sounds more appropriate for that context.