Nat, it wasn't even a DMCA claim. It was missing key components which distinguish a DMCA claim from a grumpy threatening letter. The only valid response was a blog post to shame the RIAA. Instead, shame has been brought upon github. Yall don't even read threatening letters before taking stuff offline?
There is a way forward, Nat. You can reinstate that repo today, and tell the RIAA that they cannot use your online tool. They have to send your legal representation (in Alaska to slow it down) a certified, hand-signed letter through snail mail. Make a big public show of this process, and get public mindshare on your side.