The user limits are a good thing: Let teams and individuals fork the projects. Favor more, smaller projects of better factored code, each with key trusted contributors. If your teams are large enough, you should have lieutenants performing code reviews upon pull request. Embrace the distributed model.
Whatever it is, it's probably lower than what GitHub provides. I mean, some of the largest and most promenant open source projects (with the most contributors) live in GitHub. For example, I read that Ruby on Rails 3 "consists of almost 4,000 commits by more than 250 authors".
