For the last 10 odd years, the game’s data components have been kept in Visual Source Safe. VSS is bad, m’kay. Like any piece of software, it has its merits, especially for a very small team working on a very simple project. I’m not going to turn this into an anti-VSS pejorative tho.
Moving from VSS to Subversion (and then possibly Mercurial) varies in complexity depending on your repository. Ours is ten years old and contains multiple projects, which have danced around the directory tree.