You cannot download/install any steam game offline, so NO it's NOT DRM free!
Here on GOG you also have to create an account to and be online be able to download the game. Yes, I know GOG gives you installer versions of their games but in the end you simply get a folder and can do with it what you want (I don't see the installation process as a special feature). For me it's simple: If a game isn't dependent on Steam's client (or on Galaxy in the case of GOG) and the folder is moveable from one PC to another without the need to "phone home" a game is absolutely DRM-free for me, because I'm able to do what I want with a game after purchasing and downloading it.
Most of steam games are locked with the client, and all games need to run through steam to install on-line
, yet you can make an account with gog, download your games via a library/public access independent of galaxy, and install them off-line and even transfer the install files to another computer, in short; you do not need to have Internet access in your home
to download/install the game to your system. (If you can move your installed steam client/games via public access to another off-line PC then I'll concede, which is great news for everyone, but you'll still need a laptop vs a thumb drive!)
No one is questioning the act of having to download a game, as that's a given due to the distribution method of the game being hosted on-line, but it is 100% mandatory that you install the game through steam.
Once you download the game installation files from gog, you can transfer and install the game 100% off-line.
EDIT: I agree with your statement, I'm simply illustrating this for others that may be reading this post...