Guy Trouble....help me!

My best friend introduced me to a guy at the beginning of the year. He happens to be her boyfriends best friend. We got to know each other and the 4 of us would hang out as a group a lot over the summer. The two of us flirted a lot, but he would never really "make a move." And I always wondered if it was because he knew I was going back to school in the fall. I would notice that he would flirt with other girls that we worked with, but never as much or the same way we would flirt. I tried to just focus on getting closer as friends instead of trying to push a relationship. It came time for me to go back to school, but I'm home again, for the semester and he doesn't know that yet. I found out that he has been kinda flirting with another girl that we work with. And I know that I shouldn't be jealous because we were never officially dating. I just want to know if I should just forget about a relationship with him or, should I try to see if something could happen between us.