Crisco1492: I think a few of GOG's visual novels are VERY "adult"
Ancient-Red-Dragon: No they aren't. GOG carries censored VNs.
And when censored versions aren't available, GOG simply does not carry those VNs at all.
If GOG truly allowed adult VNs, then it's selection of VNs would be vastly larger than it is now, and also, the VNs that it carries would never be censored.
Your post makes it sound like GOG proudly carries all VNs regardless of how adult they are. But that's the opposite of reality.
The uncensor patches are mostly simple things that even my mother could install, often linked in the forums of the games themselves. It's really not an obstacle. And GOG does not create a situation wherein uncensor patches don't work.
Frankly, I don't get the whole "if I have to install an uncensor patch, it's not an adult VN" perspective. In some cases it's literally just creating a blank text file. This is nothing like Illusion's censorship and the modding that Hongfire users had to do to make things playable.
Furthermore, even without actual pornographic images, the themes and descriptions can be highly adult. It's not GOG's fault that some people can't imagine things that are being described textually.