If you want to play it on your mac, and it is a different region, then just use Mac the Ripper or Handbrake to rip the DVD, then burn another copy without any region encoding.
PAL is a video format (resolution and frames per second are different than NTSC), and your computer is fine with that, it doesn't care if its PAL or not. The region encoding is an arbitrary code. If you try to play another region disk in your drive (PLAY, not just insert), then it will ask to change the region of the drive. After 5 total changes, it sticks on the last change, which can't be undone.
peace,
sam