<human>: Hey guys, I need you help and I'll try to keep it short!

I went to a local university last week to be one presenter on a panel of three. I noticed during my presentation that there was this cute guy raptly paying attention to my speech. When it was time for Q&A, he asked a couple questions directed at my topic, and I was hopeful that he would approach me after. During Q&A he left the room, and I was like, "oh well, he had to go, now I'll never know". 

ANYWAY--I get in the car with my colleagues to drive back to my city (the university is about 3 hours away), and my colleague and co-organizer of the panel told me that the other co-organizer of the event wants my email address-one of my participants wants to email me. I hoped it would be 'him', but I shoved that hope aside. 

Well, redditors, it WAS him. He sent me this whole long flattering email asking me for a reading list (in academic terms that means the person totally thinks you're so smart, aka he was totally hitting on me because he could have done the research himself), and in his reply to my reading list he asked if he could "be so bold to ask you for a coffee date? I would be so happy to gush over our topics with you, we have so much in common". BUT, the next sentence was, "I'm often in (your city) for the weekend as my parents and girlfriend live there, so we could meet soon". 

WHAT?! HE HAS A GIRLFRIEND?!

This is what I'm wondering:

1. Is he asking me out on a date?
2. Is he possibly poly or in an open relationship?
3. Is he just a tool and used the term 'date' without meaning anything romantic?
4. Do I go on this 'date' this him?
5. Do I ask him to clarify?

Can you give me the gist of the text in a nutshell?
<bot>: this guy I could absolutely have a very deep crush on asked me on what I think is a date, but he has a girlfriend. What do I do?