i just accidentally recognized that this package can be build from source and wrote an new ebuild for this package.
Created attachment 46330 [details] kunststoff-2.0.2.ebuild the ebuild itself which builds the package from source
Created attachment 46331 [details] build.xml the build.xml file for ant. used for compiling
Fixed. Available for testing as dev-java/kunststoff-2.0.2