Salut Murasame, do ctl-click on the app Phex and select see packet content, you'll see contents - open to ressources - java: the .jar are there so I think the lang folder should be put there.
Bonne chance pour la traduction en français, c'est de la grosse ouvrage comme on dit au Québec!
Ciao
edit: I told get info intead of see packet content, sorry