The API client just let you search, get popular songs, and get individual song info. There was no downloading included in the API client - if you wanted to download a song based on the info from their APIs you would have to write your own code to do that
It provides only basic search functions of course, but it is publicly documented and I'm sure Grooveshark can't complain if you use it.
I wrote a Go package for it years ago (literally, 2010 I think) and it still works fine. You get tinysong.com shortlinks, which lead to the song on Grooveshark.
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,
.url is a part of the meta info from the api - there is no downloading functionality in the api library itself. The song url is just the culmination of the song id and your session