The DMCA does make distributing circumention measures illegal, but I can't find anything in the law, or discussions of it, saying that the takedown process applies to circumvention measures. The takedown process says an ISP like Github is not liable for copyright infringement if they respond to takedown notices, which is what creates the takedown process. It doesn't say anything about circumvention measures and liability with regard to notices though.
What the DMCA says about circumvention measures:
> (2) No person shall manufacture, import, offer to the public, provide, or otherwise traffic in any technology, product, service, device, component, or part thereof, that—
> (A) is primarily designed or produced for the purpose of circumventing a technological measure that effectively controls access to a work protected under this title;
> (B) has only limited commercially significant purpose or use other than to circumvent a technological measure that effectively controls access to a work protected under this title; or
> (C) is marketed by that person or another acting in concert with that person with that person’s knowledge for use in circumventing a technological measure that effectively controls access to a work protected under this title.
It seems obvious to me that Easylist is not such, I don't think it meets A, B, or C. But it'd be an expensive court process and who knows what the court would end up doing.
In this example, it seems like Easylist has no desire to include that URL anyway, as it is not an ad server.
It may be true that Github can decide to refuse to host the thing anyway, but it's not a DCMA takedown notice process.
The whole situation is indeed a mess.