I installed the FCKEditor for a Mediawiki I run in a commerical envirement for the collection of documentations.
I had a lot of trouble installing the Editor, that's why I wanted to post how I did it in here, if somebody decides it could be usefull it would be a pleasure to me if he would use it as a guide.
1) I unziped the FCKeditor in the extensions folder of my wiki.
2) I modfied the LocalSettings.php at the end I appended:
require_once $IP . "/extensions/FCKeditor/FCKeditor.php";