Open source software

1. Computer software with its source code (human readable code) made available with a license in which the copyright holder provides the rights to study, change, and distribute the software to anyone and for any purpose. Open source software may be developed in a collaborative public manner. Voting and election systems that contain open source software have had that software reviewed by multiple, professional and amateur programmers. Open source systems are usually not free and are typically licensed like other software. Systems can be fully open source, or may have only a portion of their software open source.

Source: Information Technology Terminology, U.S. Election Assistance Commission,

2. A general term for source code and software that is licensed under an Open Source license.

Source: Open Source Voting in San Francisco Open Source Voting in San Francisco City and County of San Francisco