I had a look at NetBSD and FreeBSD: I don't think they are in a better position than linux honestly. NetBSD still uses CVS and mailinglists for contributing.

NetBSD even starts with this

An addition or change to the existing source code is a somewhat trickier affair and depends a lot on how far out of date you are with the current state of FreeBSD development.

Both might be even be worse than linux in terms of ease of contributions...

Anti Commercial-AI license