Posted September 10, 2015
trentonlf: There's no way Galaxy would know what achievements you've earned if you did not play with Galaxy running in the background. If there is a way then GOG would have had to install software into the game file that tracks what you are doing and relay that info to Galaxy when it's installed, and I certainly hope that is not something they would do.
Galaxy already "installs software into the game file", as in, the game has to implement achievement hooks. And the game can be made to track achievements internally, then submit them to Galaxy. It's not how it's currently done, though -- but it's not impossible.