(This is mostly for Nerdanel
I'm playing Theme on 2.3.x (CVS) Linux.
Some of the fixes to ToME in the 2.3.x series haven't made it in since they're in the Lua bits which have been copied into the Theme module, but otherwise it works just fine for me.
There was also a bug in modules.c which was affecting all
modules which would prevent them from working properly. I don't know if this ever made it into any released version (I suspect not). See http://wiki.t-o-m-e.net/BugReport624
I could also imagine this very same problem causing immediate crashes (and such) if you're running with some kind of extra buffer overflow protection (which OS X might do), so it's worth checking if this is what's causing problems on OS X.
EIDT: Just realized that I read Nerdanel's post as "Theme isn't working on 2.2.x"... which isn't what it says. Still the mentioned bug may still apply to OS X.