Just found this on the net:
"OS X aside,
the EFiX is definitely not an OS X install device. It’s designed to allow easily installation of almost any operating system. From legacy BIOS operating systems like Windows XP to EFI-based setups like Leopard, the EFiX module handles them all. The process is seamless and non-intrusive. This means there’s no emulation layer of any kind, and the host operating system interacts with your hardware directly."
Don't have a clue about how exactly that works, but maybe something similar with U-Boot on it could be used on PPC macs to allow installation of Amiga OS4 and/or MorphOS.
*PS* I know MorphOS MacMini port is ongoing!