GitHub is not the instigator, as far as we know (MS is apparently a member of the RIAA though). I am as amused by the clever ways to get youtube-dl back onto GitHub as anyone else, but it's protesting the wrong thing in the wrong place.
The problem lies with whichever member organizations inside the RIAA (or nonmember orgs friendly with the RIAA) convinced them to file the takedown. Most of us aren't positioned to find that out, but that's where the most can be gained. Maybe the EFF or similar orgs can help. Then we'll know what the true motives were, and how to address them.
At the same time, technological measures can show it to them that they can't feasibly take it down and that they're fighting a losing battle. At some point the RIAA will just have to accept defeat because honestly it's not that much work to defeat their DMCA takedowns.
Right now they're issuing what, 1 takedown notice to GitHub? When we make that 100,000 takedown notices, some in ROT13, some in ROT24 on an Israeli server, some in RSA encryption on a Chinese server with keys published on Russian servers, maybe they'll just be too overwhelmed with paperwork at that point.
Add some honey-pots with unrelated content and counter-sue them for circumventing encryption on copyrighted content. Because how would they know what is encrypted unless they circumvented it without permission ... unless they perjured themselves?
The problem lies with whichever member organizations inside the RIAA (or nonmember orgs friendly with the RIAA) convinced them to file the takedown. Most of us aren't positioned to find that out, but that's where the most can be gained. Maybe the EFF or similar orgs can help. Then we'll know what the true motives were, and how to address them.