HeeksCAD is a free, open source, CAD application.

Functionality: Import solid models from STEP and IGES files. Draw construction geomtery and lines and arcs.
Create new primitive solids, or make solids by extruding a sketch or by making a lofted solid between sketches.
Modify solids using blending, or boolean operations. Save IGES, STEP and STL. Printer plot the 2D geometry.
Import and export dxf files; only lines and arcs at the moment.

The solid modelling is provided by Open CASCADE. http://www.opencascade.org
The graphical user interface is made using wxWidgets. http://www.wxwidgets.org
HeeksCAD can be translated into any language.
It is possible to make Add-In modules, see HeeksCNC project.