The EFF's claim (on behalf of the youtube_dl developers) is that youtube_dl is performing the same actions as a browser as far as accessing the video file and so should not be treated differently, even if its output is to disk and not to the screen.

Under DMCA then we've had a claim, and counter notice. Despite the phrasing of Github inviting and wanting a counter notice, ultimately they are not the arbiters of legality, so their part in the process is now done.

The RIAA now has to bring the youtube_dl developers to court if they plan to keep pushing their argument, at which point we'll have the RIAA lawyers vs EFF lawyers and an eventual legal decision (with potential appeals in the process).