Interesting. So essentially they've cracked their own software and exposed it to the public on the assumption that only people who are entitled to it will install it.

I read through the comments and the forum thread, and came up with one further quotation from Adobe:

Effective December 13, Adobe disabled the activation server for CS2 products and Acrobat 7 because of a technical glitch. These products were released over 7 years ago and do not run on many modern operating systems. But to ensure that any customers activating those old versions can continue to use their software, we issued a serial number directly to those customers. While this might be interpreted as Adobe giving away software for free, we did it to help our customers. Wink, wink, nudge, nudge.
Okay, the winking and nudging wasn't really part of the quote.