I don't think it's jealousy. Obviously he wanted to be the one to hold the belt and have beaten Barao, but that doesn't mean he covets the belt if it's on a teammates waist. He can want to be the best and still be genuinely happy for a guy he helped create at the same time.
I still don't see Faber being the kind of guy to be bitter about a teammate finding success. He's come off as being one of the least selfish fighters in the sport, at least to me.