Hey Squid I'm the guy that linked you to this FS thread from the 370z forum, to answer your question yes this cable will work just fine with your 370z. The actual cables aren't linked in any way to the vehicle or tune and can be sold/transferred/passed around as needed. When someone says its "married to their vehicle" they just mean that the tune license has been transferred from the cable to their vehicle, and is still there.
The software cannot differentiate between the license that's on your ECU and the license that was on his old truck's ECU; just that they are both valid Osiris licenses... so as long as you have a valid Osiris license on your ECU you can just plug it in and as far as the Osiris software knows the cable is yours.