Long ago CDPR promised full modding toolkit to the community. They released some of that modkit, but not all of it. This will allow the community a full suite of tools to design new quests from the ground up, including posing and scripting and animation, possibly new voice line inclusion, who knows what else. Maybe text entry?
I'm glad they're finally releasing this, as we have all been waiting for it. Maybe they feel their work on TW3 is done, and recognizing their game for its cultural importance, are doing the right thing and letting the community take over for them.