Questioning if the friend is 'giving signals' sounds more hopeful to me than concerned. If you really have to be with another man, because you have 'only' been with your bf, then break up with your bf and persue the other friend.

Keep in mind, the grass is only greener on the other side of the fence because usually, a liberal amount of shyt has been applied, and if you wander in that field you'll soon find yourself covered in it. Then when you glance back from whense you came, you may realize the arrival was not worth the trip.

Take care...