As I can see YAF has already a wide variety of languages at its disposal, and always some more thanks to contributions.

I've understood how to modify the default board language by going to Admin/Board settings, but I would like to allow my users to modify this language themselves, and even fix it in their own settings...

Any solution for this?

Thanks from Beijing

It's perfect to allow the Logged user to modify his language setting.

Now I would like to allow any Guest to modify the language by clicking on some flag...

Lunch time.