The May 2013 (1305) version of SAP Solutions OnDemand Studio is now available for download on the Service Market Place.
You may use the following link to directly access the studio with its versions on the Service Market Place or you may search for SAP SOLUTIONS ONDEMAND STUDIO and drill down to the required version. Versions 1302 and 1305 can be installed in parallel. You need to use the studio version matching to your tenant version. This means that you cannot logon with the 1305 studio to a 1302 tenant or vice versa.
For information on the SDK Documentation for version May 2013 (1305) please refer to Mariannes document.