Steam but without any DRM or online requirements – that's effectively the pitch for CDProjekt's new GOG Galaxy client.
The PC software is completely optional and does not need to be connected to the internet for access, although obviously online multiplayer, achievement sharing and the like will only work if online.
The open platform will also support online multiplayer for titles using other platforms. Users can integrate their GOG.com profiles but, again, this is not a requirement.
There's a trailer below that explains the concept. There's no timeframe yet on GOG Galaxy's rollout.