I agree 100% with Adam's answer that DRM is a horrible thing, and "Digital Copy" in particular is a bad joke; see here.
However, I'll point out you can still watch your Up! Digital Copy on your Mac, even if OS X Lion doesn't support the PowerPC-based installer software on Disney's antiquated disc. I had the same issue and solved it as follows:
- Launch iTunes.
- Put the disc in your Mac's DVD drive.
- In the left navigation area, select the disc.
- You should see a page on the right asking you to Enter Code. Enter the unique activation code that came with your copy of Up!, then click Redeem.
- Authenticate with your iTunes credentials, when prompted. (Assumption: You have an iTunes account, a working Internet connection, and your Digital Copy code is valid, not expired, and not yet redeemed.)
- After authenticating with iTunes (the service), iTunes (the program) will proceed to copy the now-authorized movie content from your Up! "Digital Copy" disc to your Mac.
- Find the new title in your "Movies" library. Watch it on your Mac*.
All the details, including screenshots, can be found at:
* Worth mentioning: Even after you get your "Digital Copy" into iTunes on your Mac, it remains protected and can only be played back on a device authorized to play back purchases from your iTunes account. Consequently, you may still prefer using another extraction method on the original movie, in order to yield a liberated version of your content unencumbered with such restrictions.
Summary: DRM is still a horrible thing, even with the workaround above.
(p.s. FWIW, this method also worked (for me) for non-Disney titles such as Dr. Seuss' Horton Hears a Who!, from Twentieth Century Fox, and Despicable Me, from Universal Studios. Mentioning this in case somebody else finds this answer but has a non-Disney disc; i.e. it doesn't seem to matter whether the "Digital Copy" is Disney or not, the above method should work to authorize & copy the content to iTunes.)