Yes, if he bought $8,000 in AWS credits then he can use it as he wants, but I doubt this kind soul is trying to just throw out $8k.

This is very very likely promotional credit. They hand it out like candy.

Edit: Okay, I can see that if his approach is to use it on his own account, but for someone else's purposes, then it's probably fine. I don't think they even have any system to transfer AWS credits

Edit2: Then again I would be wary of publicly announcing that I'm actively trying to use my AWS credits for other people even though I'm not technically "transferring" them...