What do you think about me asking out a friend of a friend who as it turns out he had a crush on?
Why do you want to ask her out?
She and I had a chance to talk and she said she has a crush on me.
This sounds reasonable to me. She says she likes you, your friend of a friend hasn't taken any action. You have the right to pursue whoever you want, I think.
I don't know. I get the feeling that he still cares about her.
It would be good to talk to him about what you want to do so that he isn't blindsided. However, you have the right to ask her out if you are both single.