Good points bilbous. I think you can make strong arguments that originality is impossible except in very extreme circumstances. Ideas like Einsteins relativity took the world by surprise and were fantastically original. He wasn't even a great mathematician, but he had a knack for thinking outside the box and using thought experiments. That kind of originality is hard to find, and gets harder and harder as time goes on.
There are other aspects to the originality of PlaneShift settings that do feel borrowed but that is not necessarily the point nor is it really that important. Sometimes creating a nice atmosphere for imagination to take root is good enough, even if you borrow from others good ideas along the way.
Other things though, like using medieval paintings photo's from online for ingame paintings says to me lazy dev

Those things are not that common though so I think they do an ok job, and so long as people have the freedom to imagine and create then the possibilities are endless.