When I say OS9, I really mean OS-pre-X. Anything 680x0 based, running native or virtualized in the Mac Mini G4 (PPC). That's where interesting software is 
That's why I was thinking about Shapeshifter... It runs on RTG amigas. It doesn't hit the custom chips, it's supposedly an OS-friendly app if run in RTG mode. Or am I totally wrong here and Shapeshifter is hitting the chipset ?
The G4 would have come with an OS9 installation CD.