The OpenBIOS project provides you with most free and open source Open Firmware implementations available. Here you find several implementations of IEEE 1275-1994 (Referred to as Open Firmware) compliant firmware.
Talkware TIARA, an Openbios/GRUB/PFORTH composite, BIOS replacement. Boots an unmodifed linux kernel from an IDE drive or ethernet, using only 128kb of flash. Works with INTEL/AMD K6/2-450, SiS 530/5595 and 8139 enet. VGA & Serial console supported.
Software to allow a GNU/Linux/Mac system to be contained within one directory (folder), which allows it to be installed by drag-n-dropping it to the hard disk, removed by dragging it to the trash, and duplicated by copying it in the Finder.