Sidenote on how that game mod server was organized : the admin acted as a great monitor and organizer (which is fair enough) but also the only bottleneck in the development process. Even after 3 years of working together with the team, the only person he entrusted with limited access to the VPS simply needed to develop an online player platform (which was never deployed). In the end, all the devs left the project because our code simply wasn't getting reviewed by him and merged any more.
Our admin has great technical knowledge and took care of a lot of background stuff. He worked on game stat balancing and gave us directions to add/rework mods. He did a good job, but failed at keeping the project active by keeping his role as unique bottleneck of our development cycle even when he showed up only once a month.
I guess that's all I have to say about all of that for tonight. Maybe I'll join another FOSS project in the near future, but I don't know right now.
That's why I now know two important aspects of building a team : trust and structure.
Trust your developers, especially in small teams. Sure, a single line can break the server, but if someone's been working for three years, losing sleep to help your prod run, they probably won't mess you up. It's still fine to put in place checkpoints but then I get onto the second point : don't set up a single bottle neck that could very well cease to operate. Set up multiple trusted reviewers, not just you.