GOG has had rough patches over the years over allegations of their DRM free tenets being false. One has occurred recently when a user checked out GOG's version of F.E.A.R. Platinum and found it had active SecuROM in the expansions.
GOG is probably most well known as the digital storefront that offers games with no DRM. On the other hand, it seems like there are several definitions of DRM depending on who you ask. In GOG's case, it seems like the definition is a game that can be installed, played offline and copied as many times as a user would like.
For those unacquainted, SecuROM is one of the most dreaded DRMs in the history of the gaming industry, with some allegations going as far as claiming it literally hurt users' hardware and prevent them from using virtual drives even when they weren't related to the software that had SecuROM.
When the GOG user in question sent a less-than-polite complaint, GOG acknowledged that they weren't the first one to do so. The answer was the same one given to previous users who found out about SecuROM in F.E.A.R. expansions - it is not actually DRM but rather anti-debugging protection and GOG will not be allocating resources to remove it.
Technically, GOG have the right to refuse to remove the anti-debugging protection since that is not DRM per se. Anti-debuggers are placed so the game software could not be reverse engineered but otherwise don't interact with regular gameplay.
On the other hand, people want SecuROM installed on their PCs as much as they want a venereal disease in their body.
If it was indeed just a harmless addition that prevented reverse engineering of a 14-year-old game, it would be hard to imagine Windows 10 would treat SecuROM as glorified malware.
While some Windows 10 users don't have issues with games that have it, a simple Google search reveals the internet is littered with workaround guides that are supposed to make games with SecuROM and SafeDisk playable on Windows 10.
For clarification, F.E.A.R. Platinum on GOG works completely and SecuROM will not prevent people from playing it. The issue here stems from players not wanting anything to do with SecuROM on their PC since it can cause DRM-like inconvenience, such as blacklisting your virtual drives or creating its own registry key, as mentioned in the above-linked GOG thread.