Asteroid Zone is a Java 2 Micro Edition (J2ME) version of the classic arcade game: Your spaceship has ventured into a particularly unfriendly area of space where it must strive for survival by blasting asteroids which threaten to squash it. The ship has a powerful gun, a propulsion system (be careful with inertia!), and can teleport.
The game is free software and is available under the GNU General Public License (GPL). Basically, this means the license gives you the following permanent rights: use the software forever, distribute it to who you want, look at the source code and alter it if you are interested. The flipside is that you must grant these very same rights to other people as well if you wish to redistribute the software or publish your own software based on this software.