ralphunreal: I'm new to gog, how come there are no free to play games on gog? Also what about MMO games?
But there are:
https://www.gog.com/games?price=free&sort=bestselling&page=1 (don't could the "TBA" games into that list, it is a glitch that they are listed as free games)
If by free-to-play you mean mainly multiplayer games which are free to start but there are microtransactions if you want to do good in the game... I guess GOG hasn't seen the point yet to release any such games, especially as they pretty much require some sort of DRM, either from GOG (Galaxy) or the publisher/third-party service.
Maybe some will come at some point, maybe at some point GOG wants its own flagship "free-to-play" multiplayer game on Galaxy, like e.g. Team Fortress 2 and some others are on Steam. A Witcher team-based shooter?