I think most of my troubles were because I tried to use the latest official build which was from 25 july. I couldn't compile it because it needed jlwgl and the precompiled jar created some strange out of the jvm exceptions. Maybe it wasn't compatible with the much more recent version of jogl i used.
Almost nothing will run if you use the latest official build, because Xith3D has changed a lot in the last months. It would be really good to release a new official build.
The community build was much easier. The only problem I had with that one was that I had to edit the build.xml and remove the test that tested if my classpath existed. Somehow it didn't want to realise that I hadn't any classpath variable.
In the community builds xith3d.jar already exists, so I don't think you have to run the build script at all.