Linux on PPC is still a *great* option for older hardware.
I'm running MkLinux on two older 7100 boxen. I soon hope to try Debian on an old Quadra605.
But it seems alas most people who *can* run OSX are running it and the open support for Linux for mac doesn't have the 'eyeballs' it used to have.
It has its place with older hardware, and even works really well for newer machines. It just seems the appeal for OSX is greater than the value of speed and portability of Linux.
In reality with a proper OSX setup you can run almost all your linux software by compiling it (with minor tweaks) and running XFree86 and the other variations of Xwindows for OSX(BSD Unix).
I would *love* to have a recent kernel running on my nubus 7100's but am just happy to have such a great serverOS for those older machines. I remember the first day I got MkLinux running on the 6100 I had in 1995. It was such a rush just to see XWindows running and knowing all the power it was bringing to the hardware I had at the time.
There's still a lot of intel or nonmac specific sites running linux (they don't have OSX as their distraction). Check out
www.linuxdoc.org