Depends on your definition of an open relationship. Does that mean you want to stay in contact but be able to date other people and give it a go when you both can?
Plus, does he not want a relationship or does he not want a relationship with you? If he's not interested in a relationship period then it just is what it is and you should go on about your life and hope that when you are both in a better place that you two can make it work.
Are you all from the same place...five years is a long time to hold onto somebody that you aren't with? I don't know the guy (or you) but perhaps once you all have determined that you can't be together, maybe you should revisit life and then see whats happening if you two are ever available and in the same place.
You're still young. Enjoy it. There are other fish in the sea. And my guess is that you'll meet lots of other "the one's" before its all said and done.
Oh, and this is all because he doesn't want a relationship.