While Open Source software can often start out as free, it can incur costs later on in terms of hiring developers to build and implement applications. However, it offers opportunities for creative development and customization that are sometimes not available in an out-of-the-box CAD program.
Here are some Open Source CAD programs:
Open CASCADE Technology has been around since 1990, and is a software development platform freely available in open source. It includes components for 3D surface and solid modeling, visualization, data exchange and rapid application development.
QCAD is an application for 2D drafting, for creating technical drawings such as building plans and interiors. The source code of the QCAD community released under the GPL Open Source. QCAD works on Windows, Mac OS X and many Linux and Unix Systems.The current version of QCAD is 2.2. QCAD 3 is scheduled for release Q1 of 2011.
Cademia CADEMIA can used both by experts and occasional users. It is written in Java and runs on platforms such as Windows, Mac, Linux. CADEMIA is an Open Source product of free software licensed under the GPL. “Applications of arbitrary complexity can be efficiently implemented as Plug-Ins in Java.”
BRL-CAD is solid modeling system developed by the U.S. Army Research Laboratory (formerly known as the Ballistic Research Laboratory, or BRL) that includes an interactive geometry editor (MGED), a ray-tracing library with support for rendering and geometric analysis, network distributed framebuffer support, an embedded scripting language, image- and signal-processing tools, and a host of additional utilities.