First time in a long time I don't have any of these games. Will wait for the next "wave". You have to have the games ON steam to get them FREE.
"By popular demand, we're also bringing back the GOG Connect feature. It allows you to claim DRM-free copies of selected games that you already own on Steam. The first wave of games includes DUSK, Age of Wonders: Planetfall, Through the Ages, and Galaxy Trucker."