CD Projekt RED has finally relesed the REDkit Mod tool. The mod tools are available for free on its official website. At this point in time you need a password and username just to download the mod tools.
More information.Projekt RED announces the launch of REDkit, the ultimate set of tools for crafting non-linear role-playing adventures. Available for free via http://thewitcher.com/redkit, REDkit is based on the development tools used to create CD Projekt RED's award-winning game, The Witcher 2: Assassins of Kings.