That option does not allow you to purchase an additional license to use on an additional vehicle. It is simply to unlock your tuner if you a) bought it used and the original owner didnt return it to stock or b) you brought the vehicle to the dealer and they overwrote your tune (you need to return it to stock before you bring to the dealer in case the dealer updates your vehicle)for $100 you can get an update (additional license) that would allow you to use the tuner on 2 vehicles at once... presumably 2 of your own vehicles. On my last update a few weeks ago it was offered. I have an 07 frontier and an 05 pathfinder. I may pay for that ability in the future.
"Part Number: 4950VINULK - If the screen on your tuner displays that it is locked to another vehicle or does not seem to be working properly you may need to do a ‘Tuner Unlock’. There are a few things that can cause this such as purchasing a used tuner or not returning your vehicle to stock prior to receiving service at an auto dealer. "
If you scroll down on that upgrade it states "NOTE: This tool does not allow you to tune multiple vehicles. "