timppu: In your Steam example, if the Steam client is only needed for downloading the game, and not for playing it (even on a separate computer where there is no Steam client at all), then the game is fully DRM-free.
joppo: Sorry but I guess we'll have to disagree on this, mate. I won't make another huge post about it but you can read my point opposing your view in the paragraph you did not quote.
That part was left out as it was completely irrelevant, and I'll explain you why:
joppo: Now contrast this with a client pushed to intrude itself in the path that of the game's delivery. Why do you need a proprietary client when a generic browser is able to do the same task? Only because Valve wants to artificially create that need so they will always have a foot on your figurative house, i.e. their program running control for them in your computer.
That is irrelevant, just like a store using only a "proprietary" delivery company (like USP, or even a delivery company of their own) to bring that physical game or a vacuum cleaner to you, would be totally irrelevant to whether the product you are receiving is DRM-free or not.
You could argue why can't you pick the purchased object yourself, or use any delivery company, or the generic post office, to get it... but that still has nothing to do with DRM.
As long as the Steam client, or rather, logging into Steam ecosystem using the Steam client, is not required for using (=playing) the game, it is fully DRM-free. Remember, Steam client does not need to be even present in the PC where you play those DRM-free Steam games.
Some people seem to be completely confused of what DRM means. What client is used to enforce the DRM is irrelevant. It doesn't matter if that client is a "proprietary" client like Steam or Galaxy, or a web browser client. It is what they are doing with that client that matters.
If every GOG game you have would require you to log into your GOG account online with a web browser every time you want to play the game, would you still call those games DRM-free? I wouldn't, the requirement to log into GOG services in order to just play a single-player game is the DRM, not what client I would be using to log into my GOG account (be it Galaxy or a web browser).
Even if those games required you to have Galaxy, or a web browser, installed on your PC before the game would run... the games would still be DRM-free, as long as they wouldn't require you to log into your GOG account online with any of those clients, but you could play them in an air-gapped room with no internet connectivity to GOG servers... as long as either Galaxy or a web browser would be installed on that same system. Naturally it would be rather odd why the game would require the presence of a client software in order to run... but it would still not automatically make it DRM.