The copyright holders of Gmsh give you permission to combine Gmsh
with code included in the standard release of Netgen (from Joachim
Sch"oberl), METIS (from George Karypis at the University of
Minnesota), OpenCASCADE (from Open CASCADE S.A.S) and ParaView
(from Kitware, Inc.) under their respective licenses. You may copy
and distribute such a system following the terms of the GNU GPL for
Gmsh and the licenses of the other code concerned, provided that
you include the source code of that other code when and as the GNU
GPL requires distribution of source code.
Note that people who make modified versions of Gmsh are not
obligated to grant this special exception for their modified
versions; it is their choice whether to do so. The GNU General
Public License gives permission to release a modified version
without this exception; this exception also makes it possible to
release a modified version which carries forward this exception.