Ulvaeus is a Swedish musician, composer, and former member of pop group ABBA. 
The following quotes are from the article Björn Ulvaeus Speaks on Humanism by the International Humanist and Ethical Union:
Christer: Do you consider yourself being an atheist?
Björn: Well, I'm an agnostic leaning towards atheism. I don’t I have, and I think I cannot have, a clear view of god's existence. I do not believe in the god that is described in the Middle East religions or in any other religions for that matter. I'm not denying that there is something out there, but I don’t think that we should try to explain and understand what it might be. If atheism means that you're categorically denying God's existence, I wouldn’t go that far. The problem with fundamentalists is that they generally believe that God exists and what his wish is. I would like to say I’m a "free thinker", a better word than both agnostic and atheist. Maybe it should be reintroduced in our modern vocabulary.
He later states, "I'm not a believer myself."