Just put your PSN account with the pack on his ps3 and download it on his system and God if that's illegal then I would like to know what selling millions of people a broken product is... *point@Bethesda*
lol true enough. you also have to select the "remember password" box when you sign in, or the DLC won't work. I think you have to leave your account like that too, although I could be wrong.
you can't just transfer the data with a USB because it's copy protected(for cases like this)