Open, Messy, or I just don't get it?

A while back I found myself in a conversation with two women. It was a conversation that I wasn't expecting, between a single mother and her friend where the friend was asking the single mom about her current relationship:

(Towards the end of the conversation)

Friend: So, how long have you guys been seeing each other?

Single Mom: A few months now.

F: How is it going? You see a future with him?

SM: He makes me so happy … I think there is definitely a future.

F: (Silent)... Is it still open?

SM: Yes.

F: Wait. People get married and all that in open relationships?

F: Hold on [turns to me]. How do you feel about open relationships?

ME: I don't really know about them… don't understand it.

SM: Well, part of an open relationship is being able to have other partners if you wish that way there's no cheating or whatever. I meet anyone he's interested in, and he would do the same with me. Open relationship is about having everything out in the open...even the other people you see

ME: ... interesting. I don't think I could agree to something like that (translation: HELL NO). Even if it was just on my end I don't think I could feel right doing that.

F: Same here!

SM: Oh well that's the thing; I'd have no issue with my actions because my partner knows what I'd be doing.

ME: That's very interesting (repeating in my mind "don't judge what you don't know")

Now, I really wanted to give the "are you crazy" look, because it makes no sense to me. Granted it might work for some, but it just seems like an excuse for cheating and not calling it cheating for others. I don't know if it was just my imagination but I felt like this woman was lying to herself. Some people want something so much that they'll continue to put themselves in situations that they may not have otherwise been open to.

Over the years there have been many social changes regarding relationships and how society views them some of which have become the norm. However, consider the reality of human nature, people don't always like to share, especially personal things. In most cases, we're inclined to be jealous of a partner being with someone else and we're resistant to that partner having another relationship.

She said something about being in a fully committed relationship. My question is: How can an open relationship be a fully committed relationship? And how and when, if at all, is this explained to the children from these relationships?

Interestingly, the very next day one of my classmates informed me that she too was in a polyamorous relationship. She said that she can't give her girlfriend everything she needs and vice-versa. Her rationale being that you can't expect to get everything from just one person.

Though I may not agree with everything I hear, I do appreciate these conversations because though I tend to see myself as a pretty open minded person, these types of things challenge me. In the end I know what I am closed or open to for my own life, but to each his/her own. I just feel like with most individuals this one is a ticking time bomb.