When you hear, “I’m in an open relationship,” how do you respond?

Being single?  What does that mean to you? 
There are many shades of being single.  Being single allows one to play the field. Being single means you’re miserable on the weekends with your DVR.  Being single is just your way of holding out for that great romance that is coming your way.  Being single means I have time to hang out with friends whenever I want in any city I want.  Being single means I am not looking for anyone or anything at this time.  Being single could mean all of those for the same person depending on how one’s upper and lower brain are communicating during that day, hour, minute.  Been there, done them all.
I’ve been single for about 12 years.  What does that mean to me? Well, it means I have not used the word boyfriend in that long of a time to relate me to another male.  There hasn’t been anyone serious enough to establish a relationship.  Some sleep overs and hooking up here and there, getting to know a couple of people off and on, but the boyfriend barrier was never broken.   There have been some f-buddies and some interesting understandings between myself and a “straight” man for about 5 ½ years, but nothing stuck. 
One boundary I never desired to cross was that of the open relationship.  When I see on someone’s profile or hear them mention they are in an Open Relationship or Married, I move on to the next profile / person.  At this point in my life, I am not looking for someone that is already attached, even if it may be just for a little fun.
I had been chatting with a guy for about 2 months.  The texting was great and the pics were very "uplifting."  We both knew we would hit it off.  Schedules never coincided and I didn’t like to host at my house if it got to that point, so it was just chatting, but still getting to know each other without a face to face meeting.  One day while chatting, I glanced again at his relationship status and noticed there was nothing there.  We had both said we live with roommates so I thought he was single.   To clarify, I asked him, “Do you have a fb or a bf?”  He surprisingly did not know what an fb was so I had to explain.  Then he asked me if I wanted to know the truth. I responded as I always do, “Honesty is the best policy.”  “Well, if I tell you, you may no longer be interested,” he typed.  If he lied, I’d definitely not be interested.  He told me he was in an open relationship.  I had invested enough time in him that I was interested in meeting him, but if there was a great connection, I would have liked to pursue more than just chat and extra-curricular activities. With him being in an open relationship, it put a block on anything more occurring than just sex.  I reiterated I was looking for more than just fun.  His response was you never know …
You never know?  So was I supposed to meet up with this guy and he would see if I was better than what he had already and if so, WE could date?  His answer was basically, Yes.  He was hanging on to one option until a better one came along.  Apparently this is where his open relationship was at.  I wish I was able to show you a screen shot of the conversation, but I told the guy that I wasn’t here to compete with his boyfriend and if that is how he dated, I don’t want any part of it.  He was a little insulted that I questioned his morals and blocked me, making the chat screen disappear.  Bad option, bye bye.

I know or at least I think I know that all open relationships do not function like this.  There are several layers to some where others are pretty black and white.  It seems there are as many shades in the “open relationship” definition as there are in the “being single” category.  Some shades in each are more hopeless than others, while other shades may be filled with happiness and success. 
Maybe I should end this post as I started it, with questions.
Being in an open relationship?  What does that mean to you? 
Would you ever be in one?
Would you ever be with someone that is in one?

What do you think?