[$] The programmer's CAD: OpenSCAD

OpenSCAD is a GPLv2-licensed 3D computer-aided design (CAD) program best described as a "programmer's CAD"; it is available for Linux, Windows, several flavors of BSD, and macOS. Unlike the majority of 3D-modeling software packages which are point-and-click, the OpenSCAD website describes the project as "something like a 3D compiler", where models are generated using a scripting language. It is a unique way of approaching CAD and has many real-world applications that may be of interest.