Most Helpful Guy
Go after who you want! Open up about how you feel! And you have a chance to make him spun
Most Helpful Girl
Well I think in a lot of guys minds who do that, it's that for whatever their reason is they don't want a relationship with you right now (and it may or may not have anything to do with YOU), but they want the regular sex and feel that it's wrong to mislead you about their intentions, so they tell you exactly what they want and if you catch feelings and get hurt they don't have to feel bad about it.
If you want more, then it can suck, but being mislead sucks a whole lot more. At least when he's upfront about it you know what his intentions are. If you want more than that, don't continue things with him because you will get hurt and you will have no one to blame but yourself.
As for the whole he committed to her ht won't commit to me thing - don't take it personally. Either he thinks you're hot but doesn't see you as compatible couple, or he has his own personal reasons for not wanting to be in a committed relationship right now. It's none of your business, really.