Dating Advice: My girlfriend Wants An Open Relationship With Another Woman

Dating Question From A Viewer:

Hi there. I am a male viewer & one of your biggest fans. I know you can help me with this as you are both honest & non judgmental with your advice. My girlfriend who I live with, wants to have an open relationship with another woman. She is also OK with me having another woman as well. Is this becoming the normal way for relationships?
Susan McCord @ http://www.youtube.com/twobeavers
Andrea Wesley