To run GizmoBall, you can simply run
java -jar gb.jar 
BUT this will only allow using the AWT powered rendering. To enable OpenGL support, you must do the following:
1) Copy all files from install/toLib to the lib folder of your JVM
2) Copy all files from install/toBin to the bin folder of your JVM

Follow the configuration tips in the configurator that comes up and start the game. 
The folder boards contains our "shipped" maps.