CORS errors on local GET request; Unable to share workspace



Getting CORS errors attempting to access my c9 app from local XMLHttp request. Per community suggestion, tried to make workspace public. The editor IS public, but the Application and Files options are grayed out.
Do I need a CORS header for a GET request?

(the workspace is provided to me as a student of the Udemy Advanced SQL course delivered by Colt Steele; is a limit is placed on such student accounts?)