They are vehicle specific and he need to call DTUK he may have serious issues with his car and possibly blow his clutch or worse.
The unit is only for that exact model and not for his vehicle.
Yes you can sell them on, but they 100% need to be re-flashed to his vehicle at a cost.
Regardless if he managed to fix the problem, it is still not made for his car and needs to ensure its operating correctly
I would not risk it at all and call DTUK for them to flash it at a small cost.
I would rather be safe and pay £75 then my clutch,pistons or turbo go and have a bill for hundreds possibly thousands of quid.