I am not in anyway affiliated with GS/Escape and have 0 influence on their operations, but given what I know of them and that it only replicates what several other API libs provide, this DMCA seems really odd or a mistake?
From someone elses comment, looked at the google cache of your github repo,
> groovr.getSongFile songs[0].SongID, (err, file) ->
might have been the part they have a problem with?