The QCAD 3 source code is open source and distributed under GPL version 3 with optional exceptions. See files: - gpl-3.0.txt - gpl-3.0-exceptions.txt (if available) Hershey fonts are released under the terms described in fonts/hershey.readme. The font osifont is released under GPL version 3 with optional exceptions as outlined in fonts/osifont_license.txt. The font VL-Gothic-Regular is released under the terms of the license contained in file fonts/VL-Gothic-Regular_license.txt. Other CXF fonts in directory 'fonts' are released as public domain (all copyright is waived). Fonts in directory fonts/qt are released under their respective licenses. See fonts/qt/LICENSES.txt. Icons and documentation are distributed under the terms of the 'Creative Commons Attribution 3.0 Unported' license. See cc-by-3.0.txt 3rd party libraries and plug-ins in src/3rdparty are distributed under their respective licenses: dxflib: GPL version 2.0 or greater. See src/3rdparty/dxflib/gpl-2.0greater.txt Commercial licenses of dxflib for proprietary use are also available. opennurbs: Public domain (neither copyright nor copyleft apply). See src/3rdparty/opennurbs/readme.txt spatialindexnavel: MIT See src/3rdparty/spatialindexnavel/COPYING stemmer: BSD 2-Clause License See src/3rdparty/stemmer/bsd-2.txt Qt ships with QCAD under the LGPL Open Source license (see lgpl.txt) which confers various rights to you as the user, including the right to recompile the Qt libraries for your platform. To do that follow the documentation shown on the Qt website at: http://doc.qt.io/qt-5/build-sources.html