When ever you go to purctohase 2nd hand equipment with software, it is your responsibility to check with the software company to see if the software is transferable. just purchasing it and having a dongle doesn't mean its a legal .
I would actually argue that it is the responsibility of the person selling it that is under that obligation. Usually when someone transfers a license, there is something that they have to bring to initiate that transfer. It can't be done from the buyer, because as far as the OEM is concerned it could be a stolen license.
Now, I'm going to digress here for a few (I know, big surprise), if I'm reading everything correctly, there is something within the dongle (or maybe a read/write file somewhere) that attaches hardware info. In order for it to know that it needs to revert to trial mode. If I'm correct, that means hardware "activation"
and dongle. To me, as a preference, it's either or, not both. Now, of course, it's their software, they can do what they want, however, that isn't good in my mind. The dongle itself, limits the operation to "one user" (if everything is done on the up and up). Therefore, the dongle satisfies that condition. Even if the dongle is transferred, it's still only going to one user (unless the previous owner is keeping a cracked version for them self). The hardware attachment makes it only good on "one computer". That's different then "one user".
Most hardware activation software typically include more then one activation per serial as a lot of things can happen. Those that do just one, in my experience have the ability to deactivate in order to allow for switching computers (for whatever reason).