I was going to link some of the project docs, but then I realized they don’t answer your questions.
Team size is especially tricky, partially because it’s rather large. This page shows a graph of commits merged into the project over time, with individual graphs for the 100 contributors responsible for the largest number of commits (note that #100 was responsible for 49 commits, not a small number, and there are people with fewer commits with a massive impact on the project). This can give you some of the flavor of contribution, the history of the project is much more accurately characterised as contributors periodically coming and going, leaving behind improvements than there being a core team continuously working on the codebase (though I’ve been at it since 2012 and BevapDin has been massively prolific for nearly as long). Its almost impossible to draw a line anywhere and say, “above this line is the core contributors”.
That having been said, governance is clear, I own the repository and I’ve delegated merge rights to a dozen or so others, most prolific of which at the moment is ZhilkinSerg and longest lived is Rivet-the-zombie.
That doesnt even get into code contributions vs game data vs tilesets vs build tooling vs feature review vs documentation vs testing vs bug reporting, etc… all kinds of contributions push the game forward.
Becoming a contributor is simple, open a Pull Request on github and convince someone (mostly myself, ZhilkinSerg, or Rivet at the moment) that it’s worth merging. Everything else is coordination and communication.
