download the Desktop version for ppc computers from here.
Then just make a bootable usb or CD, and install it from there.
A PPC Mac is a loose expression, I can't speak for your computer. You wont know until you try. But, if you look at the recommended system requirements and see that your PPC Mac fits that description, then go for it! Remember make a backup of your original system so you can go back if it doesn't fit your needs in terms of performance and such.
To quote the download site:
installs on systems with less than about 384MiB of RAM (although note
that low-memory systems may not be able to run a full desktop
The download link: (check alternate install)