I have found something.
http://images.rpgnuke.ru/divinity_original_sin/concept/worldmap.pngCould this be the official map of the OS1 area?
Much stuff fits just well here and when I try to decipher it, the letters are readable.
Edit: Okay it seems to be that this map is part of the OS collectors edition! That makes it official and the map can be integrated into the worldmap it seems!

Edit2:
I was now able to decrypt the letters.
These are the words:
LATIN - English
URBS CYSEAL - City of Cyseal
ORA PRAEDATORIS - Hunter's Edge
LAPIS SACER - Sacred Stone
PALUS UMBRARUM - Dark Swamp
VALLES ARGENTATA - Silverglen
SILVA LUCULLA - Luculla Forest
PLANITIAE MAGNAE - Great Plain
SILVA LARUM - Seagull Forest?