We are not strictly monogamous, but we are not strictly polyamorous either.

Good soft porn, but that's besides the point. I think that most people are polyamorous. If you've had an affair or divorced someone because you became attracted to someone else, in a sense you're polyamorous.

We allow each other to be with other people from time to time.

Sounds like you are more Lifestyle than Poly.

I guess, I don't really know the label for our marriage. I usually call it "pagan," even though we are both atheists.

Even though it's not 100% realistic.

http://helloquizzy.okcupid.com/tests/the-polygon-test

...or for that matter if you're not a poly at-all. It's a work in progress according to the author (who isn't me), I will admit that it generally categorizes me one dimension off in one direction or another from where I know I am. In any case, I think the questions and results are insightful.

I'm just kinda baffled that you, as athiests, would use that term.

Why not "Mormon" instead? (See how silly that is?)

because I know a lot of pagan couples who are not strictly monogamous.

...but something tells me it didn't work out in the end. Hope the three who were involved are still doing okay.