I have a live cd of debian for powerpc and I am trying to install it on my old eMac that runs Mac OSX version 10.4. So how do I boot from the cd with or without using open firmware?

hmm is it a 'new world' mac or an 'old wold' mac, because if it doesn't boot while holding the C key (or whatever the key is for your machine) then you will need a bare minimum mac os 9 install (finder, system file and whatever other files needed to boot) and bootx http://penguinppc.org/bootloaders/bootx/ note your kernel will need to be here too, there may be a special kernel necessary for install only that you will have to put here for installation purposes (would be on the install cd somewhere)
otherwise if you can boot straight off the computer then it should be able to install yaboot as part of the install process

Well it doesn't boot from holding C. I figured their was some way to boot from the cd in open firmware, but I don't know what that is. Is their a way to do it on open firmware or do I need yaboot?

This site for bootx isn't working http://penguinppc.org/~benh

i provided a link
http://penguinppc.org/bootloaders/bootx/
that one works

Ya that one works but when you click on the development page to download bootx, you get this: http://penguinppc.org/~benh

and my situation is still active

Have you tried a non livecd to boot? I've installed Debian on an older G3 iMac and it booted while holding the C key. I didn't try a livecd.

like a usb stick? what do you mean exactly?

this is yer lucky day i happen to have a copy of bootx
http://www.filefront.com/17179745/BootX_Installer.hqx

A regular cd, one that is not live.