PLplot is free software that is primarily licensed under the
      LGPL (version 2 or any later version at the option of the user).  The
      exact text of that license is given in the file
      COPYING.LIB that is distributed with PLplot.  The
      free software licenses that are used for the parts of PLplot not distributed
      under the LGPL are explicitly noted in the
      Copyright file that is distributed with PLplot.