@lanodan They had to rewrite the engine though. You can even do that with proprietary commercial games provided you don't distribute the original program and files.
@lanodan I think we are going to see more decomps and enhanced PC ports of console games in the coming years.
@lanodan Super Mario 64 was decompiled and ported to PC a few years ago and has a few mods that give it HD graphics. Ocarina of Time also was ported to PC recently. There are a TON of decomp projects for console games from N64 to modern systems.
@lanodan I don't know how they get away with it. Nintendo couldn't take them down. The decomp for Zelda OOT is even released under the GPL and from what I can tell, it compiles to the original ROM 1:1. You still need to provide the original ROM for assets though.
@lanodan Well this one has a GPL in it. This one is called "Open Ocarina".
@lanodan This Link to the Past one should be safe though. The original game was written in Assembly. This was written in C after reverse engineering and is not binary equivalent and it's been ported to PC.