I have personally run Ubuntu 10.10 and Kubuntu 10.10 on two PPC machines, a PowerMac G4 quicksilver and an iBook G4 1.33ghz, the latter of the two can run Ubuntu okay but not great. Kubuntu boots on the iBook but the effects are slow (it's like watching it load each frame haha) but they do work. The PowerMac could only boot Ubuntu and it was also okay, but not good. Tiger runs way better on both. If you really want Linux on a Mac, I recommend either an older version that came out about the same time as your computer, or a new Intel Mac.