gpl-3.0-exceptions.txt

Linking QCAD libraries statically or dynamically with other modules is making 
a combined work based on the QCAD libraries. Thus, the terms and conditions of 
the GNU General Public License cover the whole combination.

As a special exception, the copyright holders of QCAD hereby grant permission 
for non-GPL compatible plug-ins and script add-ons to be used and distributed 
together with QCAD, provided that you also meet the terms and conditions of the 
licenses of those plug-ins and script add-ons.

If you modify QCAD, you may extend this exception to your version of QCAD, but 
you are not obliged to do so. If you do not wish to do so, delete this exception 
statement from your version.