I would not enable a cheater...in fact, I don't know that I could be with someone who was enabling a cheater. The potential to create drama/personal harm in MY life is too great. (Plus, if any of my partners was knowingly enabling a cheater then they are not the people I think they are.)
Re: DADT - I would be very leery of this, I don't think that it is a stable model. I would need to have very very clear PROOF that that was, in fact, the arrangement and need to know the history of how this has worked for them in the past. I would need to know WHAT the DADT actually covered and any other rules/restrictions in play. Overall, I don't think it would be worth it.
That being said, I am not all the way "out" personally. I am willing to be a "secret" from family/co-workers/public. It would be much more difficult to be a "secret" from their close friends that I might see socially. And I would NOT be willing to keep a relationship secret from MY partners/metamours/close friends.
Me: poly bi female, in an "open-but-not-looking" Vee-plus with -
MrS: hetero polyflexible male, live-in husband (23+ yrs)
Dude: hetero poly male, live-in boyfriend (4+ yrs) and MrS's best friend
Lotus: poly bi married female, "it's complicated" relationships with Dude/JaneQ/MrS (1+ years)
+ "others" = FBs, FWBs, lover-friends, platonic G/BFs, boytoys, etc.
My poly blogs here:
The Journey of JaneQSmythe
The Notebook of JaneQSmythe