darthspudius: Curious, did anyone get this to work?
teleguy: Yes.
Download
https://www.dropbox.com/s/zgsxb0pdf50hxmf/SteamOverlayFix.zip?dl=0 and extract the files to the directory where GOG Galaxy is located.
Adjust the file paths to Witcher 3 and the Galaxy Client in SteamOverlayFix.ini with notepad (if necessary).
Add GOG Galaxy to the Steam client as a non-Steam game.
Rightclick on the new Galaxy entry on the Steam client->Properties and overwrite the Target field with
"C:\Windows\System32\cscript.exe" "C:\Program Files (x86)\GalaxyClient\SteamOverlayFix.vbs" (adjust the file path if you didn't install Gog Galaxy in "C:\Program Files (x86)\GalaxyClient\")
You can now launch Gog Galaxy from the Steam client and in turn Witcher 3 from GoG Galaxy. The Steam overlay will work and Galaxy will track your playtime.
The script was found here:
https://github.com/lemasato/Steam-Overlay-for-Launchers/releases Though it would be awesome if it was included in Galaxy without this tinkering.