I have several European DVDs, and they play on the mac.
JUST BE CAREFUL:
The mac dvd player only permits 4 or 5 swtiches of regions, and then stays frozen in that last region.
If you switch a lot between region 1 or 2(Europe), get the vlc video player, free download.
So you can play one region on one player, and dvds from the other region on the other player.
I don't know about region 0 - I don't own any of those regionless dvds.