OK we've got an e-mail thread going with myself, the shelter foster, my friend (good friend of the deceased), and the woman who currently has him. She is hinting that he is being aggressive so I've asked her to elaborate on everything he has done since she's had him.
This is good news. The more information you can get about the dog's behavior, the better you will be able to help the dog - even if that means making the very tough decision you mentioned earlier in the thread.
As you already know, any rescue or adopter would want more details about the type of dog aggression the dog has displayed - is it circumstantial, only with a certain type of dog, etc. And, very important to get a better understanding about the "no kids" part as well.
Based on what has been stated so far, I do think that dog can be placed. Since it sounds like the shelter has stepped aside, maybe it will be a lot easier for you to coordinate directly with an all-breed or breed rescue.
In any event, I think it is a great that you are sticking with trying to find the best outcome for your friend's dog. It does sound like quite a frustrating experience.
Fingers crossed for a happy outcome for all involved.