Open relationships...

I have a male friend (let's call him Luke) who is happily married and they have a very open relationship. His wife has a "boyfriend" and he is allowed a "girlfriend" or whatever. Years ago, he told me about this and we got very sexually close. Luke's older and more experienced than me which made it great. Also, the fact that we both completely understood that it was just sex as friends (it IS POSSIBLE ladies).
A bit later, I moved back to school and met my current boyfriend so I stopped the sexcapades with Luke. He was bummed (as was I) but understood and was very gentlemanly about it.
Fast forward 2.5 years, ive graduated school, moved back home, still with my current bf. Reconnected with Luke and holy hell the sexual tension between us is mind blowing. My body wants him because I know how it'll feel and I know there are no emotional attachments, it's strictly for physical pleasure. But obvi, I'm not about to do anything my bf doesn't approve of.
Basically, I need advice on how to control this lust for Luke and peoples opinions on open relationships! Can you really separate lovey feelings from sex? From my experience, it's possible... Might just depend on the person.