We don't know what has happened to supersonic recently. It might have been suspended. We started using supersonic about two years ago, and really liked it. A year ago, we started to try some "innovation" on this open source project. Here is what we got:
http://swinglinux.github.io/swing/
Basically, we believe that Supersonic was developed as an embedded database system. In spite of the various advantages of an embedded database, its major disadvantage is that it cannot be shared among different processes / programs. Therefore, we developed a novel inter-process memory sharing mechanism called Swing, which is very efficient and easy to use. Then, we combined Swing and Supersonic, and created an embedded dbms, SwingDB, which can be shared among processes with lightning speed.
If someone is still following this mail list, his / her comments to our work will be highly appreciated.
Xuan Zhou
Faculty @ Renmin University of China