I voted wrong. Duh on my part, so add one to the yes cheating and subtract from the no cheating.
IMO. If one of the participants is attached to someone else, there must be some form of sneaking around to hide the affair. So, I am not seeing it as an open relationship. By open I mean by being able to be out and about freely with out the consequences of being caught. By not being able to bring that person around to your friends because they might know the parties involved. So if the single/unattached participant knows this has to go on, then they are as guilty as the attached participant.
How desperate and egotistical does someone have to be to go after someone elses spouse.