Publico respuesta muy ilustrativa del tema:
Prior to 1 January 2000 virtually all DVD-ROM drives permitted the user to change the region-code setting of the drive freely when necessary, thus allowing watching/using DVD-Video movies from all over the world (RPC-1). This was changed when the MPAA forced hardware manufacturer to implement a new technology, dubbed as RPC-2 in their drives, that only allows a maximum five change in the region-code. This behaviour affects all DVD drive and has nothing to do with the computer hardware (AMD, Intel, PowerPC) or the operating system (Microsoft Windows, Linux, Mac OS).
Fortunately, a number of resourceful programmers have developed a way to modify the firmware on some (not all) DVD-ROM drives to be RPC-1. Once a DVD drive has RPC-1 firmware applied it is possible to change the region-code of the drive freely. On the Mac OS 10 platform the region-code setting on the DVD drive can be changed using Region X software. Region X will only work on RPC-1 DVD drives. Region X will not work on RPC-2 DVD drives (ie most unmodified DVD drives). With my updated firmware (RPC-1) Pioneer DVR-107 and DVR-108 DVD-RW drives (and using Region X to change region-code setting on the drive) I can watch DVD video discs from all over the world.
Unfortunately an RPC-1 firmware update doesn't exist for the Matshita UJ-825 found in many iMac G5, iBook G5 or the HL-DT-ST (LG/Goldstar) GWA-4082B DVD-RW found in PowerMac G5 computers.
Why does the MPAA enforce this on DVD-ROM drives when just about all DVD video player purchased from home entertainment stores in Australia are RPC-1? This is very frustrating. The outcome of this is that users are limited to playing discs from one region on their computer - mostly affecting people outside the USA.
I appreciate Apple is not responsible for this problem. It would be great if Apple could pressure the MPAA to change this requirement and make it a bit more flexible for computer users.