GPL with font embedding exception:

http://www.gnu.org/licenses/old-licenses/gpl-2.0-faq.html#FontException

As a special exception, if you create a document which uses this
font, and embed this font or unaltered portions of this font into
the document, this font does not by itself cause the resulting
document to be covered by the GNU General Public License. This
exception does not however invalidate any other reasons why the
document might be covered by the GNU General Public License. If you
modify this font, you may extend this exception to your version of
the font, but you are not obligated to do so. If you do not wish to
do so, delete this exception statement from your version.
