If a friend of mine uses their forum list to newsblast all of HIS opt-in subscribers telling them about MY place and has a link directing to MY site?
I don't see how. While some/many/all on the list might consider it spammy, it is an opt-in list. And it especially would NOT be spam if through opt-in the subscribers knew that they would or could receive "news blasts" about websites of interest - such as yours. By the way, did it increase your traffic?