I read that as saying that all public GitHub repos can be copied and republished on GitHub, but that doesn't include the right to _modify_ the code. The latter

I read that as saying that all public GitHub repos can be copied and republished on GitHub, but that doesn't include the right to _modify_ the code. The latter could only be granted by a license. Of which, there is none on Auto's work. And there's none known for any of the work of other contributors. So while you can "fork" it, it's not forking it in the FOSS sense.