Finally built a Fedora Core 3 tree for PPC which should install on the Mac G5. It's at ftp://ftp.uk.linux.org/pub/linux/fedora-ppc/fc3-ppc/ (also rsync://ftp.uk.linux.org/ftp/pub/linux/fedora-ppc/fc3-ppc/)
Aside from FC3 and the current errata, it has an updated kernel which boots on the G5 and sleeps on the G4 laptops, a patched kudzu which can handle detection of BMAC Ethernet, and of course a version of anaconda which actually generates images/mac64/boot.iso. It also has a kernel-smp package for PPC32. All these changes have been submitted to relevant package maintainers and should hopefully turn up in rawhide soon, if they aren't already there.
This tree doesn't contain any of the other anaconda fixes from rawhide/FC4, so you still need to run yabootconfig for yourself before letting it reboot after installation -- see Colin's install instructions for details.