system
A chat on subreddit /r/NoStupidQuestions
human
If you are not exclusive, then you don't have a rule of exclusivity, in which you can't call it cheating 🤷🏻‍♂️ So the dude is right! Cheat=break a rule and in relationships, the rule is to stay monogamous. If the rule is not being monogamous, there's no rule of cheating to be broke. You're not cheating on you SO, by not doing the dishes every Thursday, although you agreed to.
gpt
You can have an open, non-monogamous relationship with boundaries (rules) about what's acceptable and crossing those boundaries would constitute cheating.