Generally speaking, the term open source refers to something that anyone can modify because its design / source is publicly accessible. Of course, the compound is mostly familiar to us in relation to open source software where the source code of a program is made available for use and modification as users see fit and with the main purpose of software’s performance enhancement.
The term source code appeared in the early 60s, when universities started teaching programming languages, to be first recorded in use in 1965 when the Purdue University experimented with combining source code and object code on the IBM 7090 in a system called PUFFT. The term source tree, to name the hierarchical structure of the stored source code files, was first recorded in use in 1983, the same year when Richard Stallman launched the GNU Project (he chose the name after a hacker tradition, as a recursive acronym for “GNU’s Not Unix”) to write a complete open source operating system where anyone can get the source code and make desirable changes.
“What does society need? It needs information that is truly available to its citizens—for example, programs that people can read, fix, adapt, and improve, not just operate. But what software owners typically deliver is a black box that we can’t study or change.” (Richard Stallman, Why Software Should Not Have Owners)
In order to gain support, Stallman wrote the GNU Manifesto to list the essential freedoms to software users: to run a program for any purpose, to study the mechanics of the program and modify it, to redistribute copies, and to improve and change modified versions for public use.
Soon after the launch, he coined the term free software and founded the Free Software Foundation. “Society also needs freedom. When a program has an owner, the users lose freedom to control part of their own lives….This is why we say that free software is a matter of freedom, not price.” (Richard Stallman, Why Software Should Not Have Owners)
In 1989, the first version of the GNU General Public License was published, further defining that: “When we speak of free software, we are referring to freedom, not price” and spelling out users’ permissions and obligations.
In 1991, the development of the Linux operating system kernel started, and 7 years later, Eric Raymond, a free software advocate, published The Cathedral and the Bazaar, comparing the development styles of the GNU Project and the Linux Project, where: the Cathedral (GNU Emacs) – source code is made by a small group of developers, distributed freely with each software release, The Bazaar (Linux kernel) – source code is developed over the Internet, in public, and his publication becoming one of the motivating factors that Netscape Communications Corporation decided to release the Netscape Communicator web browser as open source.
In reaction, the open source label was created at a strategy session held on February 3rd, 1998 in Palo Alto, California, and the term was later further popularised at the Open Source Summit, organised in April 1998, followed by the forming of the Open Source Initiative, a non-profit organization dedicated to promoting open source software.
And today, the popularity of open source is only to be compared with the limits of the freedoms that it comes with, with the revenue of the global open source services market expected to grow from EUR 10 Billion in 2017 to EUR 28.5 Billion by 2022.