In 2006 CodeGen, Inc released their Open Firmware implementation under a BSL like license. Their code, entirely written in ANSI C, contains the following components:
SmartFirmware: an ANSI C implementation of the IEEE-1275 Open
Firmware boot firmware standard. Dramatically reduce and ease your
firmware development and system bring-up times and costs.
An ANSI C compiler that generates Open Firmware compatible
Forth/Fcode makes it easy to develop drivers for PCI cards and PMC
modules.