I tried to do as following
1/ copy whole unzipped content to my top-level web directory
2/ Enter http://localhost/www/ , the homepage was loaded very well.
3/ My problem now is that I cannot enter text into text area because it seems dont have a text edit area here which should be included in stage-head.php as in the picture below:
4/ I think the path to checkform.php is incorrect, so I changed to ../checkform.php (just jump up one level from stage-head.php and see checkform.php). I got this error, however.
BTW, for Rule Editor page as in https://community.languagetool.org/ruleEditor2/index. Could you please tell me where I can download the source code to make my own.