LibreCAD is a free, open source 2D CAD application for Windows, OS X, and Linux. Blender is a free, open source 3D computer graphics software used to create 3D models, animation, and video games. It comes with a GPL license as per which users can share, modify, and distribute the application. MeshLab is an open source, portable, and extensible system to process and edit unstructured 3D triangular meshes.
The following are the links to install LibreCAD in Windows, Linux, and OS X: