GOG is making their own foray into the not-quite-so-finished games market. Following in the successful, if slightly controversial, Early Access from Steam, they're launching their own more particular service called Games in Development.
GOG, though, is taking a bit different approach by taking the time to curate each game that they're letting into their Games in Development program. This is the opposite of Steam, which essentially lets any game that applies for the right, enter into Early Access.
To help encourage people to try these new games, they have a great refund policy to go along with their new program, letting you get a full refund within 14 days, no questions asked. Before the implementation of the more lenient Steam refund policy, it was nigh impossible to even refund an incomplete game, even if you sort-of enjoyed it. And for GoG, there is no limit on how long you've played the game before you can get a refund.
To start off they have five specially curated games that're in-development that you can buy through them, and they also come with some hefty discounts too. Starbound, Ashes of the Singualrity, Project Zomboid, TerraTech and Curious Expedition are in the first batch, and there's plenty more on the way, they say.
GOG Galaxy is said to be a very useful tool here, letting you manually control updates and even roll-back to previous versions of these games in case something doesn't quite work right with an update. And of course all games are DRM free, the GOG staple.