Uh...there's a thing called communication. If you want to be in a non-monogamous relationship then just ask for it. Chances are you'll probably get a no the first few times, but then just find someone else until you both agree on it.
It's not that difficult really. Doing it anyway without the express permission of someone you're in a relationship with is technically cheating and then you can't realy blame the other person for hating your guts, now can you?
even polyamory is subject to limits based on each participants comfort level. some situations allow for multiple relationships outside of the primary, others only the odd anonymous tryst.
polygamy/polyamory can be a wonderful set up where everyone benefits when it is treated with responsibility and respect for the many times that the terms will be reconsidered and change.
however, in my experience (save for one) friends who claim to be poly do not treat their partner's concerns with respect and responsibility, choosing instead to use "Im polyamorous" as an excuse to fuck around however they like with no concern for the other persons feelings, or as a justification when they "are unable" to meet the accepted terms set by the supposedly open communication.
me, ive had good and bad experiences with polygamy (not polyamory because I never really had an interest in persuing more than one relationship at a time) however at the moment am happier than i have ever been in a monogamous set up
both are fine, but jealousy is an intrinsic part of our nature and is something you have to deal with that is naturally going to be more pronounced when the terms are non monogamous. Ignoring or dismissing it shows a lack of care for peoples feelings
edit: this is dyad and i really have to remember to sign my boyfriend out when posting a strong position
Even when I had "friends" I could never be with more than one during our "friendship". It was open sure, but it usually ended up that we didn't really look around either. Too many boys = too much trouble....