Well, Brian DID find out and is sending the thief a nasty email! Where do some people get the balls? All my scripts are free for everyone to use and this jackass wants to profit from work that isn't even his!
I found this forum by looking through my server referrer logs. Thanks for the info everyone!
By the way, my popup code is not meant to allow people to post their annoying advertisements, but for informational purposes, or legitimate use like site navigation. Blocking these popups would actually be quite simple. I'll see if I can find some way of stopping it from being wrongly used.