Welcome to the home of PPCForth!
PPCForth is a minimalist version of the FORTH language (for the PowerPC [tm]) which may be used as a test environment for boards, a bootloader, or even (shudder) a developement environment. I use it to boot my 403GCX board as well as loading C programs and other experiments. FORTH is particularly well suited for interactive testing as it is interpreted and as such may be extended on-the-fly. PPCForth is also rather small, weighing in at under 30K of code for everything, and under 10K for a bare-bones bootloader.
Currently PPCForth has only been ported to 403-based boards, but I am looking at supporting the 8xx series as well, as soon as I can get some actual hardware to try it on (donations anyone?).
PPCForth is licensed under the GPL.