The issue is probably due to a [known bug by Apple]
Your link is to an old issue, with 13.2
I’m using macOS 13.7.4 right now, and can download the .dmg file and it installed fine.
The OP updated Sequoia (macOS 15), and Sequoia may break things in these intermediate updates (in this case 15.3.1) If he switches to 15.4 things may be different.
macOS is becoming more and more tightly controlling as far as security.
In the Settings, under Privacy and Security, there are several possible sub-settings that may involve Terminal. One needs to go in and change what is needed. He may have to add Julia to one or more settings, such as App Management.