Monogamy or not is a choice made by individuals. Both work as long as all others involved in the 'pact' are on the same page. Honesty, transparency, understanding and sticking to your own core values (and of course, staying safe because you have that responsibility to others in the pact) is required. Open relationships cannot work without all of these first being in place.
Paco - I am amazed. For the first months after BD I was barely functional. You have achieved so much and to do so whilst going through your separation is a testament to the strength of your character.
I am over a year post BD and 9 months since he MO. I became open to the idea of 'seeing other people' some time in November, or at least not turning myself into a nun waiting for someone who might not come back. Part of the live my life directive. I am not ready for a relationship but I thought, as long as I was honest about what I could and couldn't offer, then no-one would get hurt. I saw someone for a bit - no strings. I don't feel guilty and no-one got hurt, but I decided it wasn't for me. Not ready for a serious relationship, not of the kind of person who can have a casual one ... the very definition of limbo. In any case, I am friends with the OM, but I do not see a future. I can't see a future with anyone else until I have truly let my H go. Anything else would be dishonest to myself. This has nothing to do with religion (I was raised catholic but don't practice) and everything to do with being true to myself.