Interesting article. Personally, I tend to define cheating as, any sex and/or romantic relationship carried on without the knowledge and/or consent of one's (other) partner/s. So cheating can be done "out in the open," it doesn't have to be done in secret to count as cheating. If I tell Snowbunny I'm going to date someone new, and Snowbunny says, "Please don't do that," and I tell her I'm going to do it anyway, that's cheating.
Another point for me is that it has to be sex and/or a romantic relationship for it to count as cheating. A monogamous couple can have an agreement that their five-year-old will always have a babysitter if both spouses are going to be out of the home. If both spouses go out, the last spouse to go out will get a babysitter. If that spouse doesn't get a babysitter, s/he has violated their agreement. However, I don't count that as "cheating" per se because it didn't involve having sex and/or a romantic relationship with someone else. Along the same lines, I don't usually think of breaking a safer-sex agreement as cheating, although certainly it is a violation of trust, and will do damage to the (core) relationship.
I know that others will consider any violation of any rule/agreement to be cheating and I will recognize that in a discussion about it. But personally I prefer to not define cheating so broadly. What if a poly couple agrees to fill the car with gas if it's below a quarter full? Does failing to follow through on that agreement constitute cheating? I don't think so. So, you get gray areas on what kind of rules are involved in actual cheating. That's why I define it as specifically involving agreements about sex and/or romantic relationships. I don't mean that definition to minimize major breaches of trust (such as violating safer-sex agreements). I just mean to be practical about it. Cheating in monogamy has been thought of as engaging in a romantic/sexual relationship with another person. I extend that concept into polyamory, noting that it's not cheating if you have your partner's knowledge and consent.
As for DADT agreements, I consider those to be like agreements of "knowledge ahead of time." That is, I may not specifically know that my spouse is dating another person, but with DADT, I know that my spouse is operating with that agreement in general and *may* be dating someone else at any given moment, and I have consented to that in a blanket way. So, not cheating. Although in most cases I do advise against DADT.
My 2¢,
Kevin T.
