[Kayou]

Sorry but H264 does not use JPEG for its keyframes, although it's not very different. There are a lot of differences between GIF and H264, like H264 specifies that you can use multiple reference frames, which is not the case with Animated GIF. Also H264 has motion compensation, which does not exist with GIF.

GIF basically rewrites completely a part of the picture, while the remaining part is reused. And if you consider that a rewrite of a small part of the frame to reuse the remaining part from the previous frame is just displaying a new gif on top of a part of the old one, the you can consider that it is a sequence of independent images. Maybe they don't all have the same size and are not meant to be displayed at the same position, but they are independent in the sense that you don't need a previous or future frame to display one frame.

And I wouldn't refer to GIF as lossless, except maybe if your original animation used only 256 simultaneous colors per frame. You lose information by down-sampling your colors.