I had donated way back when.
-Shut down the current instance of Subsonic.
-Ran the installer - it detected my current version and upgraded it.
-Restart the interface and bingo up an running on new version.
You will see the following under about if your license was valid:
About Subsonic
License Subsonic Premium
Version 4.8 (build 3434) – April 17, 2013
You also get this when you click the heart inspired link.
You have a valid Subsonic Premium license!