Dedee: Audio is English only, but French subtitles are availiable (via ScummVM settings).
On Steam it has different language audio settings. But i will download and see on Gog
Edit: I did find it out. But whether you wanna buy steam version (or get it online for free is another case. I dont think its anything wrong since you have bought this here on GOG in first place).
But essentially what i did to make the videos and game to be in french language is (fyi english language interface has to be a thing in italian or spanish, because for some reason in italian it has unreadable text, and in spanish it crashes once the dialogue starts so i dont know why. But Broken Sword 2 i had no problem with either of these languages. But german and french language works 100% in Broken Sword 1 method i did here atleast!
1: Download it on Steam in French (or preferred language)
2: Go to location of that folder in Steam (aka open folder Original when you go to the folder of "Broken Sword Shadow of the Templars"
3: Copy and paste files from folder named "SMACKSHI (which i assume means video in french) and folder "SPEECH". Copy and paste all files from there as a backup on your harddrive or something. Then go to where you installed the GOG game. Go to folder of "speech".. remove all files and replace it with SPEECH files from Steam one interms of language of your preference. Then go to "Video", again remove all files in there already. And copy and paste the files you got from "SMACKSHI (Video) folder.
4: Now it should play in French... though i dont know how to get the text language to change to french. Will see more to it
Edit 2: Ok so i found out how to make the language interface in your preferred language aswell as using a shortcut.
How to make shortcut, right clip on desktop, make new, shortcut. Then write
1:"C:\Program Files\ScummVM\scummvm.exe" sword1
2: Click next, now you can name it. You can name it whatever, but i name it sword1
3: To change icon to that of the Shadow of the templar logo, right click the scummvm shortcut you made, properties, and change icon and locate that icon in the GOG installation destination you made
Paste this shortcut to the root folder of "Broken Sword 1 (just to have one extra copy in case at the right place)" folder from GOG where you installed it. Essentially just remove the whole "Launch Broken Sword 1" shortcut, because that will just give you the English automatically so it will not help.
Now here is instructions you need to do to get it in French or whatever preferred language
1: In Broken Sword 1 folder from GOG. Go to "ScummVM" folder.
2: Click Scummvm.exe file.
3: Add game like you normally would, so just go back and add Broken Sword Shadow of the Templars folder
4: Edit game
5: On Language choose "French" (or whatever preferred UI language of the game
6: Click OK, exit the program. Now try to start the shortcut of Sword1.
Hopefully this should work. If you wanna do the same to Broken Sword 2? Make a duplicate of the shortcut you made and just right click and go to properties of that file, go to terminal and just write sword2 at the end of the value. And it should work likewise there too
And also just repeat the whole ScummVM process too on Broken Sword 2, and it should work likewise.
Hope this helps!
And one additional information i forgot to mention. In ScummVM settings (though this needs to be done in ScummVM in general, interms of being installed on your PC. If you want to stretch your screen so you dont get the whole 4:3 aspect ratio. Click "Options" when in ScummVM, then Graphics, checkmark "Override global graphic settings" on stretch mode pick "Stretch to window" you can also pick Fullscreen mode if you are into that.
But that should do it. Sorry for this wall of text. Hope it helped you!