This is not true. Orville Redenbacher is GMO. I know because I wrote and asked them a number of years ago. Their reply was very defensive about it.
I use this non-GMO brand:
http://www.kernelseasons.com/products/(edit) I've done a search and I see a lot of articles stating the same thing as what the link Lola posted states, that GMO popcorn doesn't exist. I don't believe it.
I remember very distinctly the defensive answer I got from O R about it. That they felt GMO was a good thing and they stood behind their products and some other blather like that.
One time, after switching to the Kernel Seasons, I ran out of popcorn once and picked up a jar of my old brand O R. I made it up and it make me so sock after eating just a few handfuls I returned it to the store.
I think this GMO popcorn doesn't exist bit is just a marketing lie, like all the others.