Yes, you're right we can't of course just translate word by word for getting French from English (look, it's what I do for writting in english, it's not really neat

) )
But so far it's still possible to have rather correct french using the LDF file. Here is a short example :
>take the river
you can't take it
here in french we only need to know the gender of the noun, and reverse it with the verb (it'd be " *You can't she take " if we translate word by word)
so I can write this :
badtake: Vous ne pouvez #quest.error.article# prendre.
and we get :
> prendre la rivière
Vous ne pouvez la prendre.
this example is quite simple, and in some other cases it can be less good. I'm looking for all the strange behaviours of Quest, and I'll try to write a report soon, I think it can apply to other language more complicated than english for this kind of syntax. But for example in Inform I can't find any problem with the translated library, so far all I got in my game written in it is good french, and it's quite flexible to adapt.
It could be a good idea to study how Inform handles the basic messages in different language (= how it can deal with syntax so it's possible to adapt it to other languages) :
http://www.inform-fiction.org/translations/of course Inform has some disavantages in comparison to Quest, and the same goes for Quest in comparison to Inform, but I think Quest can be also flexible enough to get what we want. I'll post further how it works with a foreign language.
I'm interested in using your typelib for french. At the moment apart the translation of a simple game (without typelib), I'm creating my own game in english, using typelib, so we you'll release a kind of final version of it, I may translate it, if it's not a too heavy task.