I dont believe in marriages, its just a piece of paper to 'prove how happy you are in front everybody', but more sinister is that it is a deed to keep matrimony intact that is the society under dominance of males, and male oriented indoctrination which construct gender. It is also a clever excuse for lawyers to make of thousands even millions of other people's relationships.
As for 'adultery', it is not, when both parties are agreeing with this form of sexual relationship. Adultery occurs only when one side of the couple (or trio or quads -im sure there are multiple relationships somewhere - 2 males, 2 females, got to be lol,, besides this) commit secrecy which brings in the emotional element amounting to betrayal then yes this is adultery. I suppose if say 2 couples, 1 couple are married they enjoys swinging, and the other couple is traditional, when something happens between one of each comes together, the one commiting from the traditional relationship decide to keep under the radar ( and whether caught or not) then it is adultery for the one couple... dammit this is debatable too. I for one, wouldn't but then again I dont know, never been in a relationship because so I can't comment on how real the emotion impact of such when one cheats. But I can tell you i had several firsthand experiences with women married!, and or in relationship come forward to me , but everytime this happens I declined for that I dont wish to have a conscious to break somebody's else relationship. Even one time, it backfired! she hated me for an entire 10 years, Blaming me as so I insulted her!!, i simply didnt want to face the ramification of the aftermaths of her cheat (this was in a house with 30 people all high on pot and LSD). I was so wasted but i still knew this is a no-no. But thats because i dont know what or how THEY defined their relationship, it might be totally different if i was on the ship and happened to be AT a swinger's function *and practice safe sex is a must) then maybe i might think differently i dont know but i suppose all depends on the person and situation. Naive as i might sound, I still think alot of people dont 'like' the idea of open marriages, or so rather I thnk its more about people dont understand how it might work, perhaps , just perhaps for the next 3 generations (25-30 years from now) we might be alarmed to see the popularity of open relationships, to be honest I wouldn't be surprised, hell even 'open breeding' with special screening programs for disease control we just never know whats going to be around the corner in terms of technology and ethics....so far some of us probably have heard/read of such craziness evolving at a rapid rate.
i think id stop now, and leave that proverbial cyber 2 cents on the table.