Head over to the Witcher 2 Website if you want to take part in the upcoming closed beta test of the REDkit. This is a mod tool that will make it easy to create your own Witcher 2 mods.
Here is the original bulletin from CD Projekt RED
With REDKit being officially announced now we are accepting applications from modders around the world to participate in its closed beta. In order to make the REDkit even better and more accessible, we want to hear your feedback! If you want to be involved in the process of bringing REDkit to public, don’t wait any longer and apply for your access in our beta now.
Fill out all the required information and simply click on the SEND button. We will be taking applications until the end of Sunday (30/09/2012). Soon after that, our team will make the selections and we will inform everyone about the results. Participants who will be chosen for the next stage will have a chance to test the REDkit and shape the future of The Witcher 2 modding community.