I've been using Fossil for years and TBH i don't see that "closed team" culture you speak of (though i also have almost all of my projects as "open source, not open contribution").
Fossil is a distributed version control and in fact it is "more" distributed than git if you consider that people tend to tie it with centralized services like GitHub to get more than just the VCS part. A Fossil repository contains not only the versioned files, but also a wiki, tickets/bugtracker, forum, chat room, blog/technotes - even the theme is part of it. And since it is a decentralized system, all of it are cloned when you clone the repository.
AFAIK the only limitation (hasn't really tried it myself since i only use it solo) is that for security cloned users aren't "fully" cloned so you'd need to make new users in the cloned repository - you can use the same username though (but in commits, history, etc it'll appear as different users). It'd be useful if "user" and "identity" could be distinguished so that you can have the tool know that two usernames are really about the same person.
Also Fossil works pretty much everywhere - a local server, as a FastCGI server, as a plain old CGI "script", you can even have it as a "CGI interpreter" for ".fossil" files (the repository files - the entire repository is stored in a single SQLite database file) which makes it usable with many shared web hosting services without needing root or even shell access. In a way that is the most decentralized you can go :-P.