Basically what is happening is that the superbuild builds VTK with Java enabled and then ends up copying everything into the resulting .jar file for distribution. 8.1 probably still works, but might need some globbing fixes around where the version numbers appear. See CMake/vtk_version.cmake for the version selection. That should at least get 8.1 (and even 8.2) started to be built. At that point, the *.bundle.cmake files under Projects/* are relevant for the packaging step. If you run into issues, feel free to upload logs here and I can try to help out.