I don't care if it's on GitHub at all, it's not hard to work with any arbitrary git remote. CVS would be a weird choice, but it wouldn't be a dealbreaker on its own. Fossil or some other modern alternative VCS wouldn't be a red flag or weird at all.

But I wasn't talking about contributing to the language, which is a weird standard to use here since Zig isn't interested in outside contributors. I was talking about choosing a programming language for use for some professional or personal project. I don't give a fig what version control solutions the team chooses to use if the language is good and solves my problems, and I would consider it very strange if someone tried to argue that I shouldn't use some language because they put their code on a non-Microsoft owned server.