Almost, but not quite. Humble Indie are the only ones which only contain games with a DRM-free option, while anything else may or may not be DRM-free.
Or even <OS>-Steam, <OS>-DRM-free, and <OS>-Origin. I believe there have been a couple cases where a Linux (and OS X?) version was DRM-free while the Windows one was not.

I know that and I didn't say the game wasn't DRM-free. Just that it is an odd behavior for a DRM-free game, something I wouldn't expect of it and a first time for me. Might be a matter of personal preference though, that is two matters of personal preference coinciding here although not necessarily connected: the preference for DRM-free games and the preference for keeping control of what my game does. I also don't like games to dictate the language in which I have to play them, according to my system's language, and that has nothing to do with DRM, so I guess my criticism of what this game does was misplaced and misleading in a discussion about DRM. I still stand by it though; it's not something I personally approve of, even if it is meant as a feature (for whom?). If I install a DRM-free game, I don't want it to connect to Steam, even when it can.

(I suspect, the DRM-free version and the Steam version are one and the same, and the Steam version would work if you're offline and logged out, too.)

Steam requires an online client to install the games, so you can't install the games on a computer without internet connection or if Steam is down. Call it what you want but that's causing the same problems that DRM can cause, even in those cases where the games themselves don't require Steam to run. It's debatable whether one can call them DRM-free under these circumstances. I wouldn't. IMO the "DRM-free" label on GamersGate is a lie because of this, because without the workaround the games are not offered as DRM-free installers. Online installation isn't that far from online activation. At least Steam, contrary to GamersGate, doesn't label any of the games as DRM-free, even if after installation they are (and some of them might actually work if you transfer them to an offline computer - another workaround to get a truly DRM-free game - but there are no guarantees for it).

Personally I don't hate Steam, I actually have a lot of games on that platform and I use its features, but I don't pretend it offers a similar service as GOG.

DRM-free, far as I'm concerned, is something that can be freely copied and run without any limitation, and that's true for these games. True, the need for Steam to download and install the game can be an inconvenience, and is certainly a reason to pick a store like GOG for people who are inconvenienced by it, but I don't think it prevents these games from being considered DRM-free.

Steam is DRM so Steam games are not Drm-free. Uninstall Steam and see how long you'll be able to play your games.

For some of the games on Steam you CAN indeed do what you are describing. You can unistall Steam and/or copy the games to a system that has never had Steam. This includes Half-Life 2.

But if after this you can just copy installed program - then you don't need steam anymore, and game can be considered DRM-free.

In that case, everything is DRM free then.

Not really. Some games will complain that they can't find Steam installed. So they do need steam installed (and running) to run, while others don't care about steam. Are both cases DRM free, or only those that don't care about steam? Assuming no 3rd party DRM of course.

Only those that don't care about steam can be considered DRM-free.

Steam's DRM is called Custom Executable Generation (http://www.steampowered.com/steamworks/publishingservices.php), however it is optional for the publishers whheter they want to make use of it or not. This means that if a game do not make use of CEG, you can uninstall Steam, or move the game to a different computer never having Steam installed, and the game runs fine. This means that in effect, the game is delivered DRM free via Steam (unless the game make use of a 3'd party DRM, that is).

However, if the game does make use of CEG, then it is not DRM free.

I wouldn't consider all non-CEG games to be DRM-free. Any game which uses Steam services and can't run without them has DRM far as I can see, since it requires Steam to run. It's not a big problem in many cases to remove this dependency, but I think that most games on Steam are like this, i.e., don't implement DRM as is (CEG or other) but require Steam to run.

Yes, but that's provided it will work. If the installation writes entries into the registry, just copying the program to another computer may not suffice. In any case it would be a workaround just like the one with GamersGate, it's neither a feature of nor encouraged by Steam.

installscript.vdf contains the registry entries in this case, so you can easily add them, or even add them to your backup files as a script to run automatically. Not sure if running a .reg file would be considered any more of a workaround than running a redistributable like VC++ libraries or DirectX.

Not only do they sell Steam keys but they also regionally restrict bundles now. Which is pretty much why I stopped buying from them.