This posting on AppleInsider website suggests that because of the similarity between the PowerPC based Cell processor that will power the PS3 and the current PowerPC based hardware support in Mac OS X, it will be possible to run the Apple operating system on a PS3.
There has already been some speculation that the PS3 will come preinstalled with a flavor of Linux on it’s harddrive, but this is now in question since it is uncertain whether the PS3 will ship including a harddrive, mainly for cost reasons. However the harddrive addon is likely to be an option, and since the PS3 is expected to offer media server capabilities, then the harddrive is essential.
It was also speculated earlier that Sony and Apple would form a partnership so that future Appple Mac releases could be built around IBM, Sony and Toshiba’s Cell processor, which is based on the PowerPC currently powering todays Mac. This is now unlikely since Apple have announced that they are moving to an Intel powered platform and dropping support for PowerPC processors.