It's not true that they only do this for the original owner. The disk goes with the car regardless of how many owners. The car gets a free disk update for the first two years. Since your's is an '07, you are entitled to the '09 disk as the owner of the car.
We bought both our '06 STS-V and '06 STS4 used, and we got two update disks for each car in '07 and '08 (which ended up being the '09 disk due to delays
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