Running Linux on a Mac now is about as silly as running Linux on a Sparc machine. It can be done, but there is a better Unix built for the CPU sitting in the box.

I don't know. I run MacOS X on my toilet-seat iBook, and it's close to too slow to use, not because of the CPU (466MHz G3), but (apparently) because it doesn't support the video chip in it very well.

I run Linux on my Beige G3 because I don't need multiple MacOS machines in my house and because I bought it for $75.