Good for you supporting you friend by braving coming to a forum about something that you yourself might not necessarily be interested in but to figure out how to be helpful and supportive. The world needs more friends like you! Will you be my friend too?!
Your husband has a common reaction and judgement. Its hard not to judge things we don't understand and that are not the norm. Truth is that poly dynamics are closer to the norm than ever before. Maybe the whole idea is threatening to him? Maybe he thinks their telling the two of you is in some way an attempt to pick up? Maybe he just plain feels uncomfortable knowing about other peoples relationship lives? Have you asked him any of these questions?
You are right, it isn't your business, but if you want to continue being close to them and nurturing a growing relationship then I would listen, ask questions about where they are at, button your lip when they stumble and fall and help them get up when they fall flat on their face. Embrace their differences. To me that is what friends are for.
Poly is not a lot different than a good friendship base with many people. Just as mono relationships are often based on a friendship foundation as well as a romantic one. We really aren't all that different, just more romantic love along with the friendship.
Maybe you should have a look around here. Get on the search engine and do a tag search for things that interest you? Maybe you're husband would too? At least you can be informative to him, and maybe informative to your friends.