You might check with ArtCAM to see whether they will transfer the license for free, if they want a fee for that, or if they just flatly refuse to transfer it at all. Software isn't like other products; you buy only a license to use it, that applies only to the original owner, and the manufacturer can transfer it or not as they please. If they refuse to do that, then the buyer of second-hand software will be unable to register or upgrade it, and the software might not even work on the buyer's computer.