Hi
I’ve launched JOPS 0.5 this week and yesterday I’ve finally nailed the last changes to it, including the Linux editor release.
JOPS is comprised of a particle system library and a SWING editor. It’s open source under LGPL and its hosted in sourceforge.
The Editor works both in windows and linux. Documentation and code examples will be online in a few weeks.
All textures where custom created by me and are free to use anyway you like them, comercial project or not.
Youtube Movie
http://www.youtube.com/watch?v=mlTKOsBOVMw
For more info check the official site:
http://jops.softmed.org
Sourceforge project download page:
http://sourceforge.net/project/showfiles.php?group_id=203769
Some pics of the Editor in windows and Linux:
Linux:
In Compiz - click for bigger image
With eclipse behing it - click for bigger image
Windows:
There’s an alpha version of code integration with Xith3D that was built with the help of Marvin Fr
I think the best place to start would be with looking at RenanseParticleEditor in the jmetest package in jME. It lloks cool, I have not played with particles that much, so I don't know how much of it is already implemented in jME. 
I like some of the behavior abilities you have implemented. Not so crazy about the editor… It would help if you made it more apparent which features were in use. (eg. Under GeneratorBehavior there's 24 buttons but no way to tell which of them are really being used.)
Keep up the good work.
Actually all of them are being used. The generator behavior only changes one object, the generator and nothing else, so its pretty light. Therefore, all of those attributes are active.
In the case of ParticleBehaviour, they are changing all the particles, and its quite more heavy, so i decided to give the option to activate or not each each specific attribute. Preferably you should try to use the least amount of attributes of the ParticleBehaviour. The most common to use are color, alpha, size and little more.
That's a good suggestion, in the ParticleBehaviour it should display the buttons of the active attributes in a different color. Much faster to know what's going on.
There is quite a lot to improve on the editor, but its more than enough for a 0.5 release.
I especially like the file format, it was quite a lot of work to get it working properly with JIBX, but it was well worth it. It's really fast to save and load.
The movie looks impressive and the editor looks quite complete! 
Hope to see it in JME!