Welcome to our forum.
An important disinction we make between "cheating" and "polyamorous relationship," is that in cheating, one of the persons involved is not fully informed about the situation, or is informed, but doesn't want it to be that way. So, if you are making sure to keep all involved parties informed, and, holding out for their consent, you're definitely on the "poly" side of the equation.
Don't be discouraged, though; there's people who are okay with poly, it just takes some more time to find them.
Re: religious conditioning ... that weighs heavily on some people, so you may have to be patient with your long-time friend. It's rather sad that polyamory isn't very widely accepted right now.
Anyway, I'm glad you've joined us here.
Love means never having to say, "Put down that meat cleaver!"