Like the OS 9 versions 2.0 and up, DVD Player 3.0 for X can only be installed on machines that shipped with a DVD drive preinstalled and an AGP graphics card. If you copy the DVD Player application to an unsupported machine, you will get an error message and the app will not run.
This is the MPAA breathing down Apple's neck again -- they didn't want DVD-viewing capabilities on a UNIX machine in the first place, so anything Apple does to limit access is good by them. It's absurd. I'm waiting for a hack which will allow me to view DVDs on my machine under OS X -- there are already functional hacks for OS 9.