GNU Go was the very first fully fledged free software program I had ever seen. I first saw it as an example in an old programing kit for the classic Mac which I was given for my 11th birthday. Unlike all the other examples in that programing kit, which only demonstrated how to do one thing like draw a square, I recognized this “example” as much more than just an example. It had a clean command line interface and a smart AI. I didn't know anything about the free software movement then, and I wouldn't learn until years later what GNU was, but one thing I did know is that I was given the right to actually learn how a real program is constructed and to learn how the AI worked. GNU Go was at version 1.2 at that time.
When I heard that Apple deleted GNU Go from their App Store because they couldn't possibly have people make and use programs on their iPhones like they could with their computers, I wasn't too pleased. It was bad enough that Apple destroyed my dream of owning a general purpose, portable, multi-touch computer system by making it just a giant iPod touch, but it was even worst when the only functions that the iPhone/iPad could ever have would be entirely dictated by Apple. Sure they can provide the SDK free of charge, but what use is it when you have to ask a corporation's permission to use what you make yourself?
I choose to let others learn from the programs I make, just as I have learned from others' programs. The GNU General Public License best protects that process. When Apple rejects the GPL for profits, they reject the very foundation on which I learned about making computer programs.