#3 BRL-CAD

Came into existence: Dec 16, 1983

BRL-CAD, Ballistic Research Laboratory-computer-aided design, 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. This program, which is still being worked on today, is used by the U.S. military to model ballistic attacks on vehicles.

#2 VistA

Came into existence: 1975

The oldest open-source program which is still commonly used is VistA. The Veterans Health Information Systems and Technology Architecture (VistA) is an enterprise-wide information system built around an Electronic Health Record (EHR), used throughout the United States Department of Veterans Affairs (VA) medical system, known as the Veterans Health Administration (VHA).

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