It works for me. The error you get is thrown when LT_PATH in export.sh is not correctly set to your LanguageTool directory (the directory that contains e.g. languagetool.jar).
Obviously it is wrong. I now set it to LT_PATH="…/LanguageTool-4.5" and it worked like a charm. Thank you so much. Sometimes the solution is so easy. Enjoy your week-end.
Probably this is also an easy answer for you. Is there a list of the “Wortarten-Tags” of this list. SUB, EIG, ADJ, KJ1, … It is difficult to figure all of them out and I am utterly new to this project.