I wrote it in C and used OpenGL for the graphics.
I plan to add importing OBJ files as Display Lists and custom maps. I am on a break at the moment, though. We released two tutorials with the program and it has been decided that if enough people post some cool stuff with it around the forums, work will be continued. It is kind of a way to rebuild the Zelda modding community.
We have plans for OoT and MM modifications, complete with custom enemies and custom areas. Thank you for your interest!