I have updated the MASON webpage to reflect this. I'll still be committing in SVN probably :-) but you can of course access everything in git.
Side note: porting took a long time because early versions of geomason had four very large files as demos and github won't permit files over 100MB in size. So it took us quite a bit of git-fu to successfully convert from SVN to git, then go in and strip out those files from the version history, then repack and rebuild, and then port to github. All done now.
CURRENT CONTRIBUTORS: I am presently the only person who can commit (of course). Please get with me and I'll set you up to commit on github. NO FURTHER COMMITS SHOULD BE MADE TO GOOGLE CODE. Google Code is going away in a few weeks.