I was wondering if D2D keys work with retail boxes (More specifically UT3)? since I already bought the retail box and if my brother decides to get it there is no point to have it mailed to us which takes too long and shipping costs us more where we live than buying a D2D key. (Yeah you guessed too... I don't want to download it over D2D if I already have the retail disc).
If that doesn't work, is there any other digital distribution method where I can get a retail disc-compatible key so I can just use the same disc?
So if I understand correctly, you want 1 disc and 2 keys? I don't know if you will be able to just buy a key, you will have to buy the whole game over D2D. To answer your question, I think it should work, the only d2d specific key is the activation code, the serial key should follow a pattern that will be recognized d2d or not.