Code::Blocks

The open source, cross platform, free C++ IDE

This cross-platform C++ IDE is highly extensible, making it easy to add the features you want. It includes built-in compiling and debugging capabilities, plus an easy-to-use interface.

BRL-CAD - Open Source CAD

BRL-CAD is a constructive solid geometry (CSG) solid modeling computer-aided design (CAD) system. It includes an interactive geometry editor, ray tracing support for graphics rendering and geometric analysis, computer network distributed framebuffer support, scripting, image-processing and signal-processing tools. The entire package is distributed in source code and binary form.

FreeCAD - Open Source CAD

FreeCAD is a general purpose 3D CAD modeler. FreeCAD is aimed directly at mechanical engineering and product design but also fits in a wider range of uses around engineering, such as architecture or other engineering specialties. FreeCAD is intended to make use of other open-source libraries from the field of Scientific Computing. Among them are Open CASCADE (a powerful CAD kernel, Coin3D (an incarnation of Open Inventor), the Qt GUI Framework, and Python, a popular scripting language. FreeCAD itself can also be used as a library by other programs.

Open CASCADE - Open Source CAD

Open CASCADE Technology (OCCT) is a software development platform for 3D CAD, CAM, CAE, etc. that is developed and supported by OPEN CASCADE SAS. It is available under the "Open CASCADE Technology Public License" which the developer claims to be "LGPL-like with certain differences". Despite this claim, it is not listed as compatible with the GPL license by the publisher of the LGPL, the Free Software Foundation.The Debian project considers the license to meet the Debian Free Software Guidelines and has accepted Open CASCADE into its main archive after some debate .