So, we've been sure to give back when we could. Our fork of the jme3 game engine will be available soon (although I'd recommend you go get the real thing instead of ours anyway).
But, for now we have three useful modules available on GitHub. All are available under the BSD license, meaning that you may use them in both closed- and open-source projects.
AlamodeAlamode is a super-lightweight continuous update framework for Java applications. It requires no server-side infrastructure beyond a standard web server. It quickly scans indexed local files at startup and downloads those that differ from the server's version.
We use alamode to push out updates to the Just Tactics match and chat clients.
SimmonsSimmons is a thin Java wrapper around native exec()/CreateProcess() functionality. The Java version of exec (Runtime#exec) requires that the parent process manually drain the stdout of the child process. If the parent JVM exits, then the child process will eventually stall out when its output buffer fills up. Simmons offers an exec() that truly separates the parent from the child.
We use simmons to chain between the alamode updater and the Just Tactics chat client. (Bonus nerd points if you catch the joke in the name.)
SplooshSploosh is a pure Java implementation of game-grade fluid dynamics. It uses a vorticity model to compellingly simulate vortices and swirls in the fluid medium. Since the problem is embarrassingly data-parallel, it makes use of all available processor cores to update fluid state in real time. Seriously, you should get hundreds of frames per second with thousands of vortons.
You can see sploosh-based effects throughout Just Tactics, especially in explosions.