|Both Lenny and Squeeze can be installed on PPC Macs, at least of the G4 processor family. I can't speak about the G3 processor for I have only little experience with them. You most emphatically do not need OS X. All my PowerPC macs run Debian out of the box and do not have OS X cohabiting the system.|
If your hardware is working properly, installation of Debian should be routine on your PPC Mac Mini. If you have any question about the condition of your hardware, you can download an ISO of the Apple Hardware Test disc from apple.com.
My favorite pastime is tweaking Debian for size and performance.
Chris Reich; Rochester, New York