No catch. It's just outdated (System specs call for Windows 2000/XP and Pentium III processors).
I finished install on both programs I wanted and both work fine. Serial numbers needed for each product are listed right next to the product download. It's Adobe's website and my guess is they stopped caring about CS2 now that CS6 is out.
In all honesty, I don't use Photoshop very much in my photo editing process. I bring photos into it after working them in lightroom and resize, sharpen, and that's usually it. I'll do more if I need to do localized adjustments or do some cloning to remove stuff I don't like.
Photoshop gets used more mocking up paint schemes for people on the Triumph forum. After you set up a couple base files with a ton of layers, you can do changes extremely fast.