Yup, meet the husband, talk with him, shake his hand. If they're really poly, he'll respect you for it. As for the rest, great reading at www.morethantwo.com
on a variety of topics related to your situation. I've been dating a married woman for there years, so yes it absolutely can work, but it can certainly also be hard. Unless she specifically says she wants a "co-primary", a second life partner along with her husband, chances are good her relationship with you will have certain limits in terms of time, energy, priority. Can you be ok with that? You by no means need to run out and find another partner right now, but I would strongly suggest that you yourself stay open to the notion of having more than one partner at some point.
The major players. Me, 30ish bi female. Gia, girlfriend of 4+ years. Clay, boyfriend/dom. Davis, ex/friend/"it's complicated." Eddie, roommate & fwb.
The supporting cast. Eric, Gia's husband. Bee, Gia and Eric's toddler. Dexter, Gia's lover. Helen, Eric's lover. Izzy and Nikki, Clay's partners. Liam, Eddie's husband.