Only your husband could say for sure but it sounds poly to me. The lack of communication on their part doesn't sound good. Perhaps one of them doesn't want to admit to themselves what is actually taking place. Still, I have no idea what their situation is so I can only add so much input. Just going with my hunches based on what you said.
55 y.o. unmarried straight male w/straight GF wishing to meet women for dating and relationships. Also interested in just meeting people for fun and friendships. Blog and email buddies welcome!