Hey, I bought a used cable last year. Get him to send you a screen shot of the cable manager screen and it will say in bold green letters "License on Cable" and the serial numbers etc.
See Here
A cable doesn't need to be the "Tuner" version to resell, but it is the only version that lets YOU do the tuning, any cable can have a licence on it, but only the tuner version lets you edit ROM's, other wise you have to go to a pro tuner for ROM's.
You don't need to do anything special to transfer the license to the car, it's done through the software and is completed on the first flash. It just sits in the cable until you are ready to flash the ROM, then it is on the car and no longer on the cable. If you want to sell the cable/license, UpRev or a pro tuner sends a file that flashes the car back to stock rom and puts the license back on the cable which you can then sell to anyone.
Hope this helps, I was confused initially as well.