QCAD is a free, open source application for computer aided drafting (CAD) in two dimensions (2D). With QCAD you can create technical drawings such as plans for buildings, interiors, mechanical parts or schematics and diagrams. QCAD works on Windows, Mac OS X and GNU/Linux. The source code of QCAD is released under the GPL version 3 (GPLv3), a popular Open Source license.

http://www.qcad.org/en/

http://libregraphicsworld.org/blog/entry/librecad-vs-qcad