What’s Considered “Cheating” in Non-Monogamy?

A large number of posts in non-monogamous groups ask whether or not something could be considered "cheating." Thoughtful responses challenging the notion as a concept prompted me to ask the question: Is the concept of “cheating” really of any value in non-monogamy? I’m beginning to think it might not be. We know “cheating” as it's [...]