Not initially, but yes. There is even an option to install another OS. and yellow dog linux for PS3 shipped this week. Since it runs off of G5 chips, it's very likely it would run a recent copy of Mac OSX if you modified it a bit. Also it would almost CERTAINLY install (maybe not run) the XBOX 360 OS, because they use almost identical processors. PS3 just has an extra one. The original developer boxes for both systems are/were Mac G5s. That's why the Xbox 360 gets so god damn hot! Apple never put a G5 into a laptop because of how huge and hot they were and the huge amount of power they require so expect PS3 meltdowns as often or moreso than 360 meltdowns. The G5 on my desk comes liquid cooled, are PS3's liquid cooled? They ought to be.
I predict a week or 2 from today before somebody posts up pics of running PC or Mac software on the ps3.