What's wrong with her husband?

It makes me laugh that out of this situation most people are saying "this marriage is not normal" one of my best friend is in a polyamourous relationship with the girl that he is living with, he just bought an engagement ring for her. They're tha hppiest couple I've ever seen in my life, whos to say what marriage is normal?
Just a little side note there

THIS! there is NOTHING wrong with a polyamourous relationship, as long as all parties involved are aware of the rules.

the problem with OP, that i can see, is that he walked in thinking that he was cheating... and he was OK with that. the problem is not with her husband. it's not - from what i can see - with her marriage. the problem is that the OP started something NOT KNOWING that she was in an open marriage.

OP, you need to sit down with everyone involved and talk this out like rational adults.

Yes^
So cheating is a-okay but an open marriage/poly/swingers where all parties involved are open and honest isn't? That is so messed up. I 100% support whatever kind of marriage/relationship people want to have -it's their business. But I don't encourage deception.

While I'm in a long-term mono relationship I know a fair number of poly/swingers and otherwise unconventional partnerships. In support of them I also want to add that a "successful" marriage/relationship is not necessarily granted to the couple who manages to stay together the longest (they could be miserable --it may even be abusive). Successful relationships are made from exceptional shared moments strung together over time. If you are lucky enough to have a junk-load of those great moments strung together over the long term awesome then your long relationship is also successful. But your most successful relationship might simply be the best month of your life spent with someone you once cared for. I think a lot of people are looking at this through some messed up out-dated conventional idea of what marriage/relationships are. Just because it doesn't look like yours doesn't mean it is not good or successful.

ETA: thanks BinaryPulsar

Normal means common or typical, not "good".

Man, I so thought this was gonna be like a lesbian story, but you ended out being a man...I hate you.

I thought so, too. sadksldk

Ha I hate to admit it, but I thought the same thing!

Can someone tell me where I can find a life sized care bear?

I would try to find an opportunity to talk to the husband and get some answers straight from the horse's mouth. How do you know hes really ok with everything? He might know less than you think. She could be lying to both of you. Also, he could be with another woman (or man) and not care so much about her extra-marital activities. Find out from him. How can you know if this is what you wanna be involved in if you dont know what it is?

What I don't understand is why you have posted so many details of the other people concerned? job titles of their family etc that would make it fairly easy to identify who you are talking about. No matter how open you are about your own preferences, why would you give so much information about other people on something that is deeply personal to them? I am sure this is not something any of them would wish to be debated on an internet forum.

Yes! ^ wow please stop posting personal information about this couple on the Internet!

Whats wrong with her husband?

What I find curious is the fact that her husband seems to be going out of his way to give the two of you some personal time together, as you've presented here. The possible reasons are numerous:

He may have discovered after their marriage that he is gay.

He might in fact be straight, only that his wife no longer appeals to him sexually.

He/she may be searching for a possible third person in the bedroom.

He/she might be polyamorous or swingers or are into pluralism.

He might be a man who derives pleasure from seeing his wife 'in the act' with another man.

He probably has a medical condition that has affected his ability to satisfy his wife in bed or is unable to deliver. (It is not as irregular as some might think). Some wives/husbands do interview the prospects together where they try to make the third person feel as comfortable and as part of the family as possible. A friend of mine was diagnosed with cancer and whilst she was undergoing treatment, she allowed her husband to take on a bed mate. I don't and will never understand her reasoning, but to each their own.