Polyamory and open relationships

I'm wondering what the Chewer consensus is with this, experiences, concerns, disapproval, etc. Currently, I'm married to a bisexual, polyamorous woman who I love to death, and the level of ease in our relationship in so many aspects compared to my monogamous relationships is nothing short of amazing, and it's harder to conceive putting the pressure of not allowing that woman to explore every emotional/sexual need she has and vice versa seem really selfish. Obviously, though, it doesn't stop people from staying monogamous.

Which brings me to a more specific question of how to broach the concept with someone who's strictly monogamous without setting off a red flag. The past two weeks, I've run into someone who might completely trash a budding, awesome friendship between us because she can't reconcile the fact that, despite the fact that we're attracted to each other, I'm okay with it not going any further, and another person who's going to have to be told at some point that we have been, and will probably continue to be emotionally and physically intimate with his new girlfriend.

Of course, if this is all too much, I'm sure I can find pictures of Jessica Alba in a bikini to make this thread fit in.

OK, to go into more detail, first situation, this other woman and I had been talking extensively/flirting for a little while, she obviously had an interest, and I had to say something before that went anywhere further. But we get along way too well to not want to at least be friends if that's what it came down to. At first it was no big deal, but we haven't talked in two weeks, and apparently, it's because she thinks the whole poly thing will prevent us having an organic friendship. And I'm kinda grasping at straws at how to approach the situation from here, because I would really just hate to lose her as a friend this early.

Second situation: my wife and I are both extremely close with a woman who's gotten into this whirlwind romance with a guy who's just left his ex-wife, and is apparently convinced he's going to get her to settle down, get pregnant, and drive across the country in his truck (yeah, you read that right) within the next 6 months or so. While there's many things about this guy that set off my facepalm reflex, they're both blissfully happy outside of this, more power to 'em. But at the same time, the emotional/physical intimacy between the three of us (and many of the people in her life, really) is extremely important and strong. The situation's been brought up and explained in detail, and while he's said, very calmly, that he's okay with it, even when confronted about it later, he's still very jealous and possessive whenever someone has so much as a deep conversation with her that doesn't involve him, and he seems to be moving forward with the idea that that'll all change when he moves in. Though he's apparently still okay with the idea of her having guilt-free sex with my wife. And none of us are exactly sure how to explain this respectfully without making it seem like either of us have a mind on making him feel like an outcast (he's doing a good job of that by himself, but thats neither here or there), or that any of us is stopping him from being with the person he loves.

He's coming this weekend to spend time with her, and at some point, all four of us are having dinner to discuss this, among other things. But for the first time, I'm just not sure the tone to strike, what to say to truly hammer this home, since I'm apparently the one out of the four of us who's good at confrontation. But these two situations are the first time I've *had* to truly justify this to someone who didn't automatically get it right off the bat, and I'm drawing a blank.

My wife and I met on OKCupid of all places. She mentioned she was poly was in her profile, but at the time, it had always been a concept I would throw around in the back of my mind but I was convinced it could never work in practice. I was accepting of the fact that she might still want to be with other people, and I was cool with that, but regardless, she decided to try and be monogamous with me.

Fast forward a few months of domestic bliss, we discuss it sporadically, but always in depth, and over time, it occurs to me that she pretty much lives up to my concept of what a poly relationship could be. She's willing to communicate, her priority is to her primary relationship first and foremost, everybody involved should know what the situation is, etc. She basically convinced me it could work, we had a long conversation laying some ground rules, making sure our relationship was strong enough to sustain anything that might happen, and that was it.

Not that much changes. We haven't actively gone out to pick someone up or something like that, but coming across people already in our lives who were more open that we initially thought has been fascinating to watch unfold. And the best thing in the world is realizing with all that can and has happened, afterward, she's usually the first one to call and say she can't wait to cuddle up with me at the end of the night.