Sounds like it isn't free and was never free. What they did was provide download links for CS2 products with corresponding license keys. The catch was that only those who previously purchased this product could legally use it. It's a kinda of honor system.
Yes, it's very clear on the forum that you need to already own a license to use this. There's just nothing in place to stop you from using it if you don't.
It sounds to me like they decided to decommission the activation server, then provided these binaries to somebody who called tech support because they couldn't validate their install, and the links to these binaries became public on accident. It sounds much more like some kind of internal screw up than some kind of policy decision--which is unfortunate, since many people have pointed out there are good business reasons to do this or something like it.
Should have just made CS4 free and had more people jump onto the upgrade bandwagon!