This
unfortunately named product is actually the
PPC platform's equivilent of
VMWare. It allows you to run the
Mac OS within a safe little
hardware abstraction bubble that runs on top of
linux. Thus it provides the handy feature of being able to run the Mac OS side by side with Linux on the same box at the same time, meaning you can use Linux for your
sysadmin-like tasks, drop into Mac-on-linux for those two or three mac apps you just
have to use, and still have your
linux kernel, with its memory protection and all, still
functional after the
Mac OS inevitably
crashes.
Mac-on-linux was created by some swedish company called Ibrium HB. However it is fully open-source and free and GPLed, and can be found bundled with most PPC linux distributions (LinuxPPC and Yellow Dog Linux i know of). In this respect it is maybe a tiny bit closer to a less abstract version of Plex86 (FreeMWare) than to VMWare.
Hardware abstraction is not emulation!