It's a Java Applet port of the Frozen Bubble game. You can install it automatically (menu -> Tools -> Add or Remove Plugins -> Get More Plugins) or download manually from Makagiga Home Page.
To launch the game go to menu -> Tools -> Frozen Bubble (click "Help" button to list keyboard bindings).
You must click on the game view to gain keyboard input focus
Java Applet support in Makagiga is still experimental