This is a Linux sistem for you old PowerPC Macintosh (G3, G4, and G5 CPU's)
Download the following mini.iso, depending on your computer:
G3 / G4: http://http.us.debian.org/debian/dists/wheezy/main/installer-powerpc/current/images/powerpc/netboot/mini.iso
G5: http://http.us.debian.org/debian/dists/wheezy/main/installer-powerpc/current/images/powerpc64/netboot/mini.iso
Burn it and boot it (press c continuosly until you get a prompt).
Then type:
install url=mintppc.org . Press enter.
A tip. If you are a Linux power user, when you get into the partition stage of the installer, change the ext4 partition type instead of XFS for "/". Is MUCH faster. Leave the others partitions as they are.
Finally, after the first boot of Linux Mint PPC, type these commands on the terminal, and input the password when required:
sudo chmod -x /usr/sbin/update-apt-xapian-index #disable package search engine, useless
echo "gtk-can-change-accels = 1" >> $HOME/.gtkrc-2.0
echo "gtk-button-images = 0" >> $HOME/.gtkrc-2.0 #no icons on buttons
echo "gtk-menu-images = 0" >> $HOME/.gtkrc-2.0 #no icons on menus
sudo apt-get update; sudo apt-get install iceape vlc #light www browser, old VLC player
sudo apt-get install firmware-linux-free firmware-linux-nonfree rcconf #better 3D aceleration on some ATI cards
#iceape is a fast web browser
sudo rcconf #enable/disable services
#disable cron, bluetooth (if you don't need it) and exim, (AND NO MORE IF YOU DON'T KNOW WHAT ARE YOU DOING) press [spacebar] to enable or disable services , [q] to quit
sudo reboot
More help at www.mintppc.org