Would it be backstabbing if I was talking to a guy my friend was recently talking to?

My friend was talking to a guy for a while, they were “together” but not dating. After a while she stopped talking to him, and moved on to different guys and is currently talking to someone different. The guy my friend use to be talking to is now starting to talk to me, and I’m sure its not in a friendly way, he obviously wants something more than just being friends. My friend has moved on from him, and doesn’t talk to him anymore. But she has a tendency to keep all the boys she once talked to, to herself. For example she gets mad when other girls talk to the guys she has associated with. And me being her friend I don’t want a guy to get into our friendship. She’s already moved on and talking to other guys, and she doesn’t care for him anymore. I enjoy talking to him. Should I continue talking to him? Would it risk our friendship? Please help! Thank you all very so much!