If you Google around Adobe released a statement saying that those CS2 downloads and provided serial number are for customers who bought CS2. Adobe switched off their activation servers but made the serial numbers available to mitigate that.
Adobe's actions and disclaimer on the downloads is interesting - they seem to be using vague legal language, e.g. using "may not" instead of "must not", deleting posts on its forum that claim using those downloads without a license is illegal, etc. To me it looks like they're just trying to discourage it somewhat officially; given their rather lax stance on piracy, they probably believe it's better that someone uses unlicensed CS2 than something non-Adobe.
They are undoubtedly for those customers, but legally you have to enforce copyrights to keep them. There is no way that Adobe could argue that they are still enforcing copyright restrictions on the binaries of CS2.
You're confusing copyright with trademarks. Trademarks must be defended if you want to keep them (this is logical: if other people are using them, they are no longer a mark of your trade). That doesn't apply to copyright; it's an entirely automatic process.
You are right. Thinking it through you can of course put a restrictive license on stuff that is publicly available, otherwise of course open source would not work. What Adobe may have done is confused their original license terms by posting a download with key, so a court is very unlikely to award more than nominal damages should Adobe get annoyed with it being used, but you are perfectly correct, their copyright still holds up.
If you're happy using software you don't have a license for, why not grab CS6 off of the your favorite torrent site.
People bitch and bitch about DRM (and god knows I do as well), but as soon as a company tries to release software without any licensing hoops or other checks, people jump all over it and shout "Hey everybody, this company isn't going out of their way stop me from using their software, it must be free!!!!" Just because you can download and run some piece of software from a companies website doesn't mean you have a license to freely use it.
It seems like you are ignoring the context in which this is happening. People aren't going for the CS2 or cracked CS6 because they want to, they are going for it because the service they have paid for is gone.
I am recommending this on a thread for people who can't use their paid for software from Adobe. Sure, some other people might use it as well, but seeing as Adobe have already calculated that they can afford the risk before they started offering CS2 plus serials for download, I don't think I need to worry too much. As far as downloading a cracked version, well there is no way I am going to recommend to people to try out random cracked stuff off torrent sites.
It works pretty well in Wine as well, if you fiddle with the settings.