Sapan,

The good folks over at the MIT-licensed Haiku (formerly 
known as OpenBeOS) are also working on OpenFirmware
support for their PowerPC port. (Though PPC has been on the 
backburner lately, x86 being the main priority at this point.)

FWIW, here's what I hope is a relevant part of CVS:
http://cvs.sourceforge.net/viewcvs.py/open-beos/current/src/kernel/boot/platform/openfirmware/

Not sure if this is interesting:
http://cvs.sourceforge.net/viewcvs.py/open-beos/current/src/kernel/core/arch/ppc/

Regards,
Jonas Sundström.               www.kirilla.com