Right now, you can't, but hopefully a Mac coder who's current with both Intel and PPC OS X application porting will someday stumble upon this game.
The game is OpenSource technically, other than a couple little things that still aren't sorted out to protect from cheating, but I'm sure that if a respectable person comes along requesting CVS access they might get it.
I play Quake 1-3 on my MacBook all the time, and dpball would rock too man, I hope there's a port soon.
