Well, you used to be able to do that with macOS, but I think they stopped that from happening in the last few years.

https://en.wikipedia.org/wiki/Darwin_(operating_system)#Open...

Gitlab may one day also decide that their core is too large and too useful to let everyone play with it too.

Also, you're not strongly disagreeing with me. I said the same thing, the only difference is that you can get most (but not all) of the useful things from whatever GitLab currently considers its core to be.