If there are outdated entries, feel free to comment in that forum thread as it still seems to get regularly updated. Doesn't change that it happened, though. It required a public backslash for GOG to remove HITMAN GOTY after all.

I'd say hiding part of the content of a single player behind online connection is a type of DRM. Even by your definition, you won't be able to back up installer that includes that content. It's absolutely a DRM, if not for the entire game than for definitely for DLC.

But even if you dismiss those and multiplayer games, there's still more in that list that DEFCON and Multiwinia. Any game that requires Galaxy has as much DRM on it as any that requires Steam. Admittedly, not all of those seems to be intentional. Some of them are due to the bugs, but it still prevents players from just backing up installer and sharing it with friends. It's nice that GOG helps with patches for old games, but apparently when it comes to Galaxy requirement, the official solution usually is “just use Galaxy”.

In the end, the claim of the previous poster was that GOG doesn't allow selling games with DRM, which even a single example proves wrong. GOG may do a lot of good for preservation, but that doesn't mean they are not beyond reproach.