I've looked up abbreviations of Nécessite.
only thing I could find was Nécess.
It gives us: "v3.8, 100 MB, Nécess Java 8+" (only one letter longer than the english version, so it should fit) but I'm not sure on the accuracy.
"LanguageTool est un correcteur grammatical libre pour:" followed by a (partial) summation of the supported languages on the second line. (while this changes the flow of the text compared to the english version, it should be much easier to read.)
(best to let this be done by someone who actually knows French)