By the way i'm french too, and i'm a backer as you are. ^^
Everything is ok for me, except the fact i'm waiting for the translation of the Mac version.

Available on my account page :
Purchased on Jul 1, 2014 Downloader mode
Faster, more convenient downloads! Install now
My game: Windows Mac
Preferred installer version:
Original game: Divinity: Original Sin - game
Windows installer, French 6.3 GB 2.0.0
Update (game version 1.0.47) 66 MB 2.1.0
DLC: Divinity: Original Sin - Source Hunter

So, i'm afraid the issue concerns your proper account... frown
Have you send GOG an email?