You can take the course for free, but you won't get credit for it. From the Udacity blog:

"Living up to our promise to always provide a free path to high-quality education, we are also offering these courses free of charge as conventional MOOCs, but this path will not include instructor access, additional support services, or a path to college credit."

Blogpost: http://blog.udacity.com/2013/01/sebastian-thrun-udacity-anno...