It is possible to install CS2 and run it without a license, but it is not free. Adobe shut down their license servers a couple of years ago and posted information “for customers who paid for CS2” to download a version of CS2 which didn’t require activation. Yes anyone can download and run CS2 without paying, but it is not legal unless you purchased CS2. They just don’t have any protections in place.
It is also important to note that CS2 was designed for Win XP and Mac 10.5 (?) and it does NOT run well (or at all) on newer OSs.
-Robert