This could be as easy as releasing the tools they used for development when developing the game.
Most game studios are similar, in reusing and improving a whole development architecture and systems across many titles. I would not agree with making them release that, even an older version. That's a big competitive moat for some studios.
I think if a community group wants to PAY to operate a server, that's quite reasonable. And then you still end up with a fight about how much to charge. But I don't think handing over server code is the right move.