Are 1201 takedown notices even supposed to be a thing, or were they just invented by the RIAA and/or other overly enthusiastic copyright holders? I was under the impression that DMCA notices were for the removal of infringing content, not alleged anti-circumvention tools. That's what the law seems to specify. The notification and takedown process is specified for infringement of copyrighted works, not distribution of…
I find the GitHub announcement deeply unsatisfying for that reason: GitHub is unilaterally inventing a body of "law" that's going to meaningfully govern the lives of tons of developers in the future. This body of rules is "law" and not law because the entity doing the enforcement is GitHub and not some government, but GitHub still has enough power to cause injury if it decides it doesn't like you.