It's more like gamersgate, really. Once you make an account, you can access a page that shows all the games you own on GOG. From there you can download the games as often as you want, but you'll have to download the GOG downloader first. When the game is downloaded you install it to any directory you want, and run it like you'd run any game. You don't have to run it through an application, like Steam, and there's no copy protection.