Open-source software

A screenshot of Manjaro running the Cinnamon desktop environment, Firefox accessing Wikipedia which uses MediaWiki, LibreOffice Writer, Vim, GNOME Calculator, VLC and Nemo file manager, all of which are open-source software.
The logo of the Open Source Initiative

Part of the broader term free and open-source software.

- Open-source software

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Eric S. Raymond

Raymond at Linucon in 2004
Raymond at the SouthEast LinuxFest in 2019

Eric Steven Raymond (born December 4, 1957), often referred to as ESR, is an American software developer, open-source software advocate, and author of the 1997 essay and 1999 book The Cathedral and the Bazaar.

Fork (software development)

In software engineering, a project fork happens when developers take a copy of source code from one software package and start independent development on it, creating a distinct and separate piece of software.

A timeline chart of how Linux distributions have forked

Free and open-source software may be legally forked without prior approval of those currently developing, managing, or distributing the software per both The Free Software Definition and The Open Source Definition:

Open Source Initiative

Trademarked OSI "keyhole" logo

The Open Source Initiative (OSI) is the steward of the Open Source Definition, the set of rules that define open source software.

Free and open-source software

A screenshot of free and open-source software (FOSS): Linux Mint running the Xfce desktop environment, Firefox, a calculator program, the built-in calendar, Vim, GIMP, and VLC media player

Free and open-source software (FOSS) is software that is both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the source code is openly shared so that people are encouraged to voluntarily improve the design of the software.

Open-source software development

Process-Data Model for open-source software development

Open-source software development (OSSD) is the process by which open-source software, or similar software whose source code is publicly available, is developed by an open-source software project.

Free software

Computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions.

Linux Mint. An example of a free-software operating system running some representative applications. Shown are the Xfce desktop environment, the Firefox web browser, the Vim text editor, the GIMP image editor, and the VLC media player.
This Euler diagram describes the typical relationship between freeware and free and open-source software (FOSS): According to David Rosen from Wolfire Games in 2010, open source / free software (orange) is most often gratis but not always. Freeware (green) seldom expose their source code.
Diagram of free and nonfree software, as defined by the Free Software Foundation. Left: free software, right: proprietary software, encircled: Gratis software
Richard Stallman, founder of the Free Software Movement (2002)
Copyleft, a novel use of copyright law to ensure that works remain unrestricted, originates in the world of free software.
Although nearly all computer viruses only affect Microsoft Windows, antivirus software such as ClamTk (shown here) is still provided for Linux and other Unix-based systems, so that users can detect malware that might infect Windows hosts.

Although both definitions refer to almost equivalent corpora of programs, the Free Software Foundation recommends using the term "free software" rather than "open-source software" (a younger vision coined in 1998), because the goals and messaging are quite dissimilar.

Open-source license

Type of license for computer software and other products that allows the source code, blueprint or design to be used, modified and/or shared under defined terms and conditions.

License compatibility for derived works and combined works of a developer's own code and externally developed open-source-licensed code (adapted from Välimäki 2005 )

One popular set of open-source software licenses are those approved by the Open Source Initiative (OSI) based on their Open Source Definition (OSD).

Netscape

American independent computer services company with headquarters in Mountain View, California and then Dulles, Virginia.

The original green and purple Mozilla mascot, a Godzilla-like lizard which represented the company's goal of producing the browser that would be the "Mosaic killer"
Netscape logo 2005–2007, still used in some portals
Netscape Communicator 4.61 for OS/2 Warp
Netscape Navigator 9.0

In January 1998, Netscape started the open source Mozilla project.

Open collaboration

Any "system of innovation or production that relies on goal-oriented yet loosely coordinated participants who interact to create a product of economic value, which is made available to contributors and noncontributors alike."

Value or price

It is prominently observed in open source software, but can also be found in many other instances, such as in Internet forums, mailing lists and online communities.

Tim O'Reilly

Founder of O'Reilly Media (formerly O'Reilly & Associates).

O'Reilly in 2017

He popularised the terms open source and Web 2.0.