The “Zelda Demo” has been done by Alex Pagliaro aka Dark Cloud. Here is a small extraction from the readme:

This is a small demo of sprite animation, backgrounds, and sprite+background collision using graphics from the Legend of Zelda. It works pretty well except for one small bug which I can’t seem to figure out. But you probably won’t encounter it. I might make the source code public if I clean it up a bit first.

http://www.gbadev.org/