Not really a question, but a little heads-up for those confused: when Kent mentions having explained the TextureAtlas add-on in the rock lesson, he really means it's part of the "shading the Sci-Fi helmet" course. You'll find it here:
https://cgcookie.com/lesson/consolidating-uvs-with-texture-atlas/
Thanks for the clarification ccarloscd! No doubt several users will wonder the same thing.