The Witcher website reveals that CD Projekt have released the 1.3 patch, which is stuffed to the gills with the adventure editor, and a new quest-o-thing, The Price Of Neutrality. Apparently the new adventure is about two hours long, with multiple endings. It explores the activities of others Witchers, as glimpsed only briefly in the original game.
The D'jinni editor, meanwhile, is the tool that CD Projekt used to build the original game, so you're now going to be able to use all the original assets from the game to create your own Witchering projects. Should you have lashings of spare time, natch.