I agree with you and this is what I currently do.

However, apparently the Steam version allows limited previous versions selection, so I read that Squad managed to push the 1.0.5 (previous stable) from the list of available versions in Steam...

"Thats result of ignoring essence of DRM" one could note, but that would be right, but a bit rude.

I personally do have pre 1.1 installer backups for KSP downloaded before the update, but that is wholly beside the point. The issue at hand here is one of reality matching rhetoric. Galaxy users have access to functionality that non Galaxy users do not, despite this being readly achievable without the need of a separate client in order to do so. This makes the statement that Galaxy is and will always be "totally optional" an extremely dubious assertion. Whether by design or by ineptitude, this is no longer a claim that GOG can make in good faith.

I see your point here and like i said above, it would be nice for the non-Galaxy users to be able to downgrade, but don't forget that it's not GOG's fault that KSP is not stable for some people (or some people don't like the newer version for some reason), the blame is on Squad*. Galaxy it IS** optional - you can install, play & update the game you bought without using Galaxy.

* of course, i don't actually blame them for anything - in fact i'm glad they continue to support & upgrade the game we all love to play and such complex game can't be devoid of bugs, especially during the whole transition to Unity 5 phase.
**so far and i would like to believe that this won't change in the future.

The same could be said about achievements; Galaxy users have achievements and what else but those who don't use Galaxy, don't have them. That doesn't make any difference on the "optional" part for me, even though non-Galaxy users have sort of reduced functionality.

Having said all that, i would like to believe that if someone really has a problem with the current version of KSP, support would be able to fix it for them by actually providing them a link to a previous version of the game. Anyway, time to have fun with 1.1.2 - i hope there won't be any critical bugs this time! :)

I totally agree with you on this point.

Also with the rollback function in Galaxy it's like that:
Galaxy will update a game automatically whenever an update is available. So having a rollback function is basically a function to counter this.

If you do not use Galaxy, you download the installers yourself. Which means that until you delete the older installer(s), you have your own rollback archive. That's the beauty of DRM-free: You can keep whatever you like for as long as you like.

And while I do not think it would be THAT complicated to offer this archive on the GOG Library (but I am not entirely sure IF it would as I do not work for GOG), I do not think it's that big of a deal. As pointed above, you can keep whatever version you like - it's up to you. If there's an update of a game I just keep the old version until I am certain that the new one is working as intended.

I don't think it would be that complicated as you say, but there are a number of issues that could arise from such a decision:

- How many previous versions will they keep? Only the exact previous one or another two for example?
- For how long?
- Would this be done only for specific games? If yes, how would GOG decide what games should be included in that rollback feature?

Mhm... good points indeed. I guess for Galaxy this is a bit easier as only the updated files need to be stored in different revisions. I guess this cam heavily differ from game to game but surely needs less space on the servers as preserving the full installers in all sorts of different versions.

However I guess GOG could simply offer the previous version of a game (in terms of KSP it would be 1.0.5 that was deemed very stable) and keep for a "grace period" of 3-4 weeks after the release of an update to give users the chance to grab it and revert if needed.

- two known stable releases: oldstable, stable and optionally current if beta.
- lifetime
- all games

That was long answered in Linux package managers such as apt/dpkg or portage.

in this case there might be an easier answer:
On steam SQUAD usually keeps several older versions available (at least that used to be the case).
Since the developer already plans for this, GOG could just ask SQUAD how this should be handled :)

The Galaxy client does not perform magic. Even if we assume that the different versions are stored as delta patches, only applying changes where necessary, then it's a relatively simple procedure to make it possible to apply those patches without the client as well. The client functionality in this regard can certainly be replicated by a standalone executable, even presuming that it's not that way on the back end of the client anyways.

When it comes to software installation, if it can be done in the client, then it can be done without the client. The only barrier here is the availability.

This is not a functionality that needs to be restricted to the Galaxy client. That's what separates this from things such as achievements, chat, in-game overlays, or anything else one tends to find in this or other game clients. I'm not trying to say that it requires no effort at all on GOG's behalf to make this possible outside of the client, only that it is disingenuous of them to put that effort into the client software and not for non-client user access as well. Downloading and installing games is at the very core of GOG's basic service that essentially all users require, client or no. If there are game versions are downloadable only via the client, then this, in effect, turns non-client users into second class users. If the assertion that the Galaxy client is and always will be totally optional is anything more than marketing lip service, then care needs to be taken to not let key functions like this be confined to the client.