Upstream is: http://www.libsdl.org/
But, probably there are RPM sources packages of the library or maybe even binary PPC RPM packages, but i don't know more, i've only used a RedHat distribution nearly ten years ago...
Anyway, i suspect you can't get ZSnes to work on PPC, it's heavily IA32 assembly based.
FWIW, there are Debian packages for PPC of SNes9x:
http://packages.debian.org/unstable/games/snes9x-x, in other words, on Debian SNes9x is a couple of click away (and in Gentoo is probably a matter of emerging it)... (=