'freeCAD' is created with the open source StCAD:
3D CAD Framework for Smalltalk and a private motion simulation
program. All the source code is in Smalltalk which is a pure object
oriented programming language. The development environment used is
VisualWorks which is
also open source. To learn more about Smalltalk, please
visit
http://www.whysmalltalk.com
http://www.goodstart.com