None do, because GIF is nolonger free, and GD was designed to be a free tool.
If you are into doing illegal things I'm sure google can supply you with the required information. But note: as the GIF creators nolonger supply their code free of charge, using it without a paid license is illegal, and allthough the chances of them catching you are small, if they do, you are in for the high-jump.
Anyway, PNG and JPG are much better than GIF.