From Larry Lessig's blog, a major victory for open licenses:

I am very proud to report today that the Court of Appeals for the Federal Circuit (THE "IP" court in the US) has upheld a free (ok, they call them "open source") copyright license, explicitly pointing to the work of Creative Commons and others. (The specific license at issue was the Artistic License.) This is a very important victory, and I am very very happy that the Stanford Center for Internet and Society played a key role in securing it. Congratulations especially to Chris Ridder and Anthony Falzone at the Center.

In non-technical terms, the Court has held that free licenses such as the CC licenses set conditions (rather than covenants) on the use of copyrighted work. When you violate the condition, the license disappears, meaning you're simply a copyright infringer. This is the theory of the GPL and all CC licenses. Put precisely, whether or not they are also contracts, they are copyright licenses which expire if you fail to abide by the terms of the license.