The ambiguity of the situation is the only clear thing about it.
Adobe could settle this one way or the other by stating on the download page, "This is for legally licensed software owners only." However, Adobe has not done so.
No one has come forward with a statement that Adobe contacted him/her with that download link and serial by email, etc.
When a person leaves his car door unlocked and ajar and theft of property occurs, the car owner is partially guilty for the theft as he/she left the door ajar and no effort was made to prevent the theft: Indeed, the owner winked at the thief and took no reasonable step to ensure security.
Here, the software is old and the seller has left it in the open, and even provided a key to anyone happening upon it. Moreso, Adobe advertised the link.
While anyone downloading the software without a legally obtained license is doing so in a less than honest way, I wouldn't go so far as defining it as a theft or a crime. Here the temptation is winking at a person who under other circumstances might well have made no effort to obtain that software. Adobe is equally or more at fault, and I don't think Adobe cares one way or another about any unlicensed download.