What is open source software? | IBM

Until the mid-1970s, computer code was seen as implicit to the operation of the computer hardware, and not unique intellectual property subject to copyright protection. Organizations programmed their own software, and code sharing was a common practice.

The Commission on New Technological Uses of Copyrighted Works (CONTU) was established in 1974 and concluded that software code was a category of creative work suitable for copyright protection. This fueled the growth of independent software publishing as an industry, with proprietary source code as the primary source of revenue. As personal computing brought applications to every corporate desk and many households, the market for software became intensely competitive and software publishers became increasingly alert to infringements of their property rights.

A rebellion of sorts against the restrictions and limitations of proprietary software began in 1983. Programmer Richard Stallman chafed at the notion that users could not customize proprietary software however they saw fit to accomplish their work. Stallman felt that “software should be free–as in speech, not beer,” and championed the notion of software that was freely available for customization.

Stallman founded the Free Software Foundation, and would go on to drive the development of an open source alternative to the AT&T-owned Unix operating system, among other applications. He also innovated the first copyleft software license, the GNU General Public License (GPL), which required anyone who enhanced his source code to likewise publish their edited version freely to all.

Eric S. Raymond’s 1997 essay titled “The Cathedral and the Bazaar” is seen as another watershed in the free software movement. Raymond contrasted the closed, top-down approach typical of proprietary software development where all development was handled by a core group (which he called The Cathedral), versus open, freely-shared public development over the Internet (The Bazaar). Shortly after, Netscape Corporation released their Mozilla browser code as open source, and the open source movement gained legitimacy.

Because many felt that Stallman’s term “free software” inaptly emphasized “free of cost” as the main value of the software, the term “open source” was adopted in 1999. The Open Source Initiative was created to advocate for it; the organization also has established ground rules for the industry via the open source definition, and hosts compliant open source licenses. Today, the terms free software, open source software (or OSS), free and open source software (FOSS) and free/libre-open source software (FLOSS) all refer to the same thing: software with source code available for public use and customization.