I think that your friend has the right to be a little irritated by you. Put yourself in her position. If you had been going out with a guy and he screwed you over, and you broke up. Then your friend started liking him. Wouldn't you feel a little betrayed and a little angry? It's crossing a big line to pursue things with a friends ex, especially if you have not spoken to your friend about it first. It can be painful to see a friend take interest in someone that you once had feelings for yourself and were in fact in a relationship.
I would suggest that you simply approach your friend about this. Ask her if she is bother by the fact that you like her ex boyfriend. Tell her that you are sorry that you didn't ask her about it first and that you didn't mean to hurt her. Tell her how much you like this guy and if she doesn't want you to pursue anything with him then you'll just have to respect that or stop being friends with this other girl.
As for the actual guy, i personally cannot tell you whether he likes you or not as i am not there experiencing it. I would suggest that you ask him about it. Ask him whether he likes you. Or you could be more subtle by simply inviting him somewhere, sort of like a "subtle date". Without directly saying "Do you wanna go on a date".
I wish you the best of luck and hope that everything turns out the way you want. If you need to message me then please do.
-Cara