Hi Pilou,

"My index html is lang.set("FR");" <<This is correct.>>

"My lang.js is var lang = { LANGUAGE: "FR" } " <<<This is "incorrect." Leave it as: var lang = { LANGUAGE: "EN" }>>>

I temporarily went to MoI Options, and edited the moi.ini file to read, under [UI] as Language=French
With index html: lang.set("FR");, and leaving your lang.js as downloaded, with var lang = { LANGUAGE: "EN" }
no other modifications were needed to get French Node language.
There is no need to add the French words to the EN section, lines 159+ in your post.

- Brian
(These are my personal observations and tests and opinions:-)