Well, Linus still ultimately pulls from his lieutenants' repos though. Nobody has direct push access to Linus's repository but Linus (if I recall, at least.)

Well, Linus still ultimately pulls from his lieutenants' repos though. Nobody has direct push access to Linus's repository but Linus (if I recall, at least.) That's functionally equivalent to github's pull request system. What's better about Linux is the fact that Linus cares enough to keep things up to date and have a functioning release process with freezes, etc. All of that can be done in github, it just requires maintainers to put in the effort.