The free software movement's most important license -- version three of the GNU General Public License was unveiled by the Free Software Foundation late last month. It comes roughly 16 years after its wildly successful predecessor, GPLv2, became one of the most used software licenses ever. Today, approximately three quarters of the world's free software packages are distributed under GPLv2. GPLv3 has some big shoes to fill. The differences between GPLv2 and GPLv3 are simultaneously tiny and tremendous.