I don’t think that “implied license” you’re referring to holds up in the courts.

Looking at that ruling, it seems the case you linked to hinged on a fact not applicable with the Stack:

>Field had actual knowledge of the Googlebot. He also was aware of the ways to prevent Google from either listing his site at all or listing it but not providing a link to the cached version. Instead of opting out, however, he chose to allow Google to both index and provide a link to the cached version.

For the AI dataset, (A) did the person know their work was being collected by this group and for this purpose, and (B) did they know of a way to prevent that collection?

It is not clear to me if they are _only_ using GitHub as source. The Stack explicitly mentions they are using Software Heritage as source and Software Heritage definitely sources from repositories that are NOT stored in GitHub (and never have been).