I mean, may I install two copies, in two directories, set different languages for each, and make them use same database "AND" albums folder ? Is there any other instructions that I should follow if this is doable ?
Cagri
Yes, this is doable. You would neee to create an extra config table in the database, and then change the conifg table designation in one of the installs init.inc.php. You would also only run install for one of the galleries. You would need to create the config.inc.php file for the other by hand. You would need to make the albums folder for one install a symbolic link/shortcut to the actual albums folder.
Alternatively, you can just provide links to the same gallery with the language selector attached (http://www.mygallery.com/CPG/index.php?lang=french).
Another option is to use the anycontent block to provide a language selector dropdown box.