timppu: So the same question to you: if GOG games required you to always log into your GOG account with a web browser before you can either install or even run a GOG game, would you consider them DRM-free? After all, you'd use this open https protocol for it, so no DRM? You are in control because of the protocol/tool?
Let's be clear. There's obviously got to be a way to differentiate between people who own something and people who don't. You can't just let anybody download any game, any more than people would be allowed to simply walk into a games retail store and walk out with the game. Paying for the game in a retail store provides that way to differentiate, while authentication provides that for online purchases. There simply isn't any way around that. It isn't about control, it's about the system functioning properly at all, the same way that the HTTP protocol is necessary for an online shop to exist. DRM is not about basic functionality such as that, it's about control, so no - logging in as a requirement on GOG is not DRM.
As I said before, being able to download (deliver) your games with several different methods may be more convenient, but it still has absolutely nothing to do with DRM. DRM discussion is relevant only when you have the game in your possession, how the service or publisher tries to control your usage of it at that point. When the game is still in the store, or on Steam/GOG servers, it is not yet in your possession.
Possession =/= ownership? I'd say that DRM kicks in once you own something - you should have full control over something as soon as you own it.
As you say, DRM is about control over your usage. Steam controls that usage, both to install the game you have purchased (which cannot be avoided) and in many cases it's required to also play.
GOG doesn't offer a choice to get your purchased games on burned CDs that they deliver to you, or even go to their office in Warsaw and copy your games to an USB memory stick yourself. Yet, people don't consider it DRM that they don't offer such game delivery options, but you actually have to go log into your account online, for a delivery.
Retail stores don't generally offer downloads for products you buy there, either. No, it's not DRM, nor is lack of physical delivery mechanisms from GOG DRM. It's simply difference in delivery. There are multiple ways of delivering a product, and most shops don't want to/can't support them all. That has nothing to do with any effort to control your product.
timppu: Also when we discuss about the DRM-free Steam games (after delivery), to me personally the important point is that they are not officially supported as DRM-free products. So if you have any problems trying to run them without the authentication, you are on your own. And like I pointed before, that "DRM-free Steam games" list has lots of such remarks, like that saving or reloading a game doesn't work without a client, or only part of the game works without the client, or you need some third-party tool to make it DRM-free.
Agreed. there is lack of support for installing or playing any steam game except through the steam client. That you can do that at all with some of them is a workaround of the DRM inherent in the steam client.