If you remember a couple of months ago, GOG inaugurated a service where you can redeem certain games from them if you already own them on Steam. They had a few games up for a while and then the thing went quiet. They just put up a few new games for a duration of a week (6 days remaining as of this writing).
They're the old versions 1 to 3 of Master of Orion, a classic 4X game series. This coincides with the release of the new MoO.
This was just a little heads up in case people followed the service for a while and then gave up. It's looking like the offers are going to be pretty rare and over quickly, making it easy to miss them. But they're still keeping it alive at least.
The last time it got overloaded quickly and took a long time to process some requests. With fewer games on offer this time this probably shouldn't happen.
I'm not at that excited about the new MoO myself. I'll have to check it out some time, because I did love these types of games back in the day. The only thing that'd make me actually excited would be a faithful remake of the old Master of Magic, but that's a pipe dream. And, I guess Civ VI could turn out decent.
https://www.gog.com/connect
It's just a wild guess on my part, but they might make a similar offer for the older games in the Witcher series when this one comes out.
http://www.polygon.com/2016/7/6/12106196/the-witcher-3-game-of-the-year-edition