Copying code. That's seems more duplication for strictly the original intended purpose.
The important thing with copyright is whether you copied, not how you copied. So copying a work by looking at it and then duplicating it is still creating a derivative -- or could be of you reproduce a substantial part of the creative work.
Now, AWF's position seems tenable to me as there are apects of the photo that are not the _creative_ input of the photographer; namely the likeness of the subject. Duplication of those aspects is akin to duplication of the API: is duplication of apects that are not the creative work of the creator of the first work (in one case because those aspects are technical, in the other case because those aspects are just the features of a person's face [the photographer didn't creatively produce those features, unless they're a plastic surgeon!]).
Now, Warhol did copy. Unlike Google he didn't need to copy that particular work for interoperability reasons. To me the fact that any photo would have embodied the subject's features equally well means Warhol had no need to copy this one. That makes AWF's case distinct from Google v.