Yo Tim, according to someone on a forum I linked to this post: >>>>> The link to Doukutsu (Cave Story) in there was for the Linux version. I was pleased to find out that there's also a Universal (non-Rosetta Intel) version available. Mac Download (universal) and the Mac Translation Patcher
Anything open-source written in Java or SDL automatically is for Mac as well, no? It's a matter of compiling it on one, then playing it, but it's all there and as available as the open-source Unix games.