I'd find someone else to get involved with, this mess is too complicated. If you didn't have your doubts you wouldn't be asking the question. Being the third wheel is not the situation you sound like you want. Even open relationships have a catch... you're sharing with everyone. If the person is looking for an out in their relationship- great- let them get up the guts to get out on their own without involving you. If they aren't interested in leaving their spouse to be with you, you are just a diversion to what ever problem they are having with their spouse. If they are willing to leave their spouse for you, then a commitment doesn't mean a whole lot to them. -BTW, I'm married, so my opinion is a little biased...