Clicking on the French language brings you to:
http://lifeisfeudal.gamepedia.com/Planc ... ois_dur/frSo it does bring you to the French page, it just hasn't been filled in yet.
But yeah if you look at the links of everyone language, you'll see that each has its own language code.
German: lifeisfeudal
-de.gamepedia.com
Polish: lifeisfeudal
-pl.gamepedia.com
Russian: lifeisfeudal
-ru.gamepedia.com
However the French language doesn't:
http://lifeisfeudal.gamepedia.com/AccueilSo the French pages are using the base English wiki, with just custom page names.