There was an update of the driver software in september 2007, but it looks like there still is no mac driver available.
Maybe the card can work in a mac with a pc emulator, if there is a pc emulator on the mac that is capable of accessing pci slots directly?
Catweasel ain't cheap. I bet it costs more than what he got his 500 for.

Will the pci catweasel work in a mac running UAE? (is there a mac version of UAE?)
Sparing that, for PCs, ubuntu linux will boot to a desktop right off the cd. I'm not sure if there's a mac version of ubuntu, but maybe yellowdog does the same thing. From there, you could use modprobe to load the linux catweasel drivers into the kernel. That should work. Lots of money and time just for a workbench disk. It's probably better just to buy a set off of ebay.
brian