Additional permission under GNU GPL version 3 section 7

If you modify this Library, or any covered work, by linking or
combining it with CGAL (or a modified version of that library), the
licensors of this Library grant you additional permission to convey
the resulting work. Corresponding Source for a non-source form of
such a combination shall include the source code for the parts of CGAL
used as well as that of the covered work. 

