Yeah, I think there's a lot of functionality that yousei intended to put into the program that he never got around to. My understanding - I think from the readme file - was that the whole thing was a project he was working on at one point for a programming class. I guess he finished the project and then never finished the program. Or dropped the class, maybe?
Anyway, copy and paste work within the program, so what I usually do is just go tile-by-tile, highlighting what I want to use, copy, then select where I want it to be and paste. It's a wicked-slow process, but fortunately for me, I'm not making any huge world map edits.