I think that model works well when it comes to code, but I don't think the non-free software movement ever really figured out how to deal with services and data. Even if GitHub was completely 100% GPL Free Software... the user accounts and everyone's comment history and stuff lives on a database somewhere. The servers are running somewhere. That's where the community is.
Even if you could take GitHub and spin up your own fork running the exact same software, the community isn't there. The interactions aren't there, the history isn't. It's like building a clone of your childhood house and wondering why your young parents don't magically appear in it.