Can I translate some mods or the launcher in french?

I see some translation made for some mods and also for the Lucas mod launcher but nobody made french's translation. I know there are some french people who want to play some mods in french and I'm able to do it. So I want to know which tool should I use?

If you'd like to translate any mods in french, asking the authors of the said mods is the way to go. As long as you have their permission, you're allowed to post them in here as well.
As for translating the mod launcher, you should check out this page. It gives an explanation on how translating the launcher goes, as well as giving two example language files.

Do you think this will interest many people?

I'm not sure. There are a lot of people playing the French version of the game (same for the other languages) so maybe there might be some people.

I have already started to translate the Lucas mod launcher I've already done 1/3 of the work

Is donut mod already translated into French?