adaliabooks: Well... if I understand how these things work (or should work, maybe that's my mistake) the deluxe edition is just the base edition plus DLC (as I have Lords of Xulima deluxe and that's how it works) so I would hope if you own the deluxe edition it would show as DLC...
ElTerprise: But if the Deluxe DLC only consists of goodies it just shows those. I added a screenshot from the Technobabylon entry in my libary to my previous to show what i'm talking about.
adaliabooks: Edit: And it shouldn't matter whether there is a game or whether it's just extras (I think... XD)
ElTerprise: But apparently it matters. Otherwise it would be recognized as DLC, wouldn't it?
Not sure... it could be because it's a deluxe edition and they don't all behave as expected, it could be a broken property, or it could be as you suggest that the option I'm looking at is for game related DLC only and packages of extras don't set it to true (in which case I need to find a new property to check on...)
Or, knowing GoG, it could be any number of reasons... XD
Anyway, thanks for the help. I'm probably going to leave it there tonight and come back to it tomorrow and see what I can figure out.