Time4Tea: I'm not sure it can be explained by simple incompetence, when a store that claims to be 'DRM-free' has been notified of a DRMed product and apparently has no interest in doing anything about it. Incompetence I can forgive (to an extent), but to me that seems more like wilful dishonesty.
The possible solutions include simply de-listing the product, which can be easily done by GOG alone. If GOG is turning a blind eye to DRMed products on their store (and not for the first time), then they are complicit.
richlind33: GOG does have a flexible definition of DRM-free, so it's all good from their standpoint, I suspect.
That's the point. GOG is by now officially OK with anything publishers want to put in their games. Only if a big outcry happens, they reconsider. Before the massive push-back from the community, GOG was totally OK with the DRM in Hitman, for example.
Ponczo even officially stated that GOG believes that developers/publishers should be allowed to protect their games however they want, as long as that doesn't affect the game in a major way. Whatever 'major' means. Locking an entire DLC behind DRM apparently isn't major enough.