I registered on community.languagetool.org. I can see a list or rules and seem to be able to edit rules. (I haven't had the need, but the page loads for me.) However, the rule writing utility produces an error. I have an account and was logged in at the time.
The link/button on http://community.languagetool.org/rule/list?lang=en labelled "Add New Rule" produces and error for me on http://community.languagetool.org/rule/index. The error message is empty. The title of the page says Grails Runtime Exception.
The link with the problem is at the bottom in the red box.
The result after clicking it.