Kristian: IMO, what is needed is a cross platform, open standard(with a reference implementation liberally licensed ALA the MIT license or Apache License 2.0) API to do the kinds of things that Steamworks does(cross game chat, achievements, matchmaking, mod sharing, cloud saving etc).
ET3D: The problem is that these things require a service. Some of them would work without a specific service, but matchmaking, or the social aspect of achievements, require a central site and for players to be a member of that site. At that point it doesn't matter much if the API is an open standard or not. (It matters a little, but I don't think it can become practical.)
Yeah some of those are services but an open standard would allow competition among service providers. As is some games are not coming to GOG or have inferior GOG versions because of Steamworks or the like. If GOG and/or the developers/publishers could choose to offer those services themselves for the GOG version or even do so for all versions that would allow more games to come to GOG.
An open standard with a permissively licensed reference implementation would also allow all game developers to use such API(and in the case of services offer or access them) no matter the license of the game.
Currently games using for example the GPL'ed id Software engines(id Tech 1 - 4) can't use for example Steamworks, but they could use an open standards Steamworks competitor. If GOG were to develop such an open standard, it would take out one of the main advantages of Steam.
Steamworks is and the community on Steam is one of the reasons why I sometimes can even by enthusiastic about games using Steam.
The GOG Downloader can't compete with Steam at all on those fronts. GOG desperately needs an (optional of course) client with those kinds of features.
Imagine if GOG had an optional client that due to open standards allowed you to chat with people running Origin, Uplay, GFWL, Desura, etc!
That allowed any developer on the planet to support cross-game chat, achievements etc no matter the platform(OS and hardware platform), distribution channel(Steam, GOG, Desura, etc) or license of the game?
Ofcourse the major obstacle to such a scenario would be adoption. So the scenario above with GOG -> Origin chat would require EA to be on board. I don't know how likely that would be. But it would be awesome if GOG would at least try.
Edit:
I should add this would give us a much needed divorce between digital distribution services and the actual features of a game. Digital distrubution services could then compete on pricing, selection, customer service and what kind of DRM if any they use.
Edit2:
As is now you have to make a choice between DRM free gaming and features such as achievements, etc. This would eliminate the need to make such a choice. A *very* good thing IMO!