There was no DMCA issued! All that indicates there was is the message received by OP, which claims dropbox as both issuer and recipient of a DMCA notice. That

There was no DMCA issued! All that indicates there was is the message received by OP, which claims dropbox as both issuer and recipient of a DMCA notice. That makes no sense -- unless, as claimed by dropbox, it is simply an automated message generated by error. I think a lot of people in this thread are under the impression that dropbox issued a DMCA request to github, which wasn't even what the OP was claiming.