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What is Free & Open Source Software (FOSS)?

To understand what FOSS is, we first need to understand a small amount about copyright and licenses.

Copyright is the right to copy certain kinds of artifact (e.g. written works). The only party that may copy a copyright artifact is the copyright holder, or a party given explicit permission (directly or indirectly) by the copyright holder.

A license is the permission granted by a copyright holder to copy a copyright artifact. A license can place conditions upon the permission to copy.

So, you may not copy a copyright artifact unless either:

FOSS (Free & Open Source Software) is software whose source code is licensed under a Free or Open Source license.

It follows that all FOSS is copyright, because otherwise it could not have been licensed. The copyright for a given piece of free or open source software is typically held by the developer that wrote the software (though copyright ownership may be transfered, or even shared).

And so, all FOSS can be said to be property. In other words, all FOSS is proprietary (so the use of the word proprietary to distinguish FOSS from non-free/closed-source software is inappropriate and misleading).

To sum up: FOSS is proprietary software whose source code is made available under a free or open source license.

What is source code?

Source code is the stuff that programmers write and maintain. In most cases, source code must be translated into a different form before it can be executed. Let us refer to this second form as "object code".

Object code is designed for efficient execution by a computer, and is not designed for people to read. Changes to software are made to source code, which is again translated into new object code before use. It is extremely unusual to directly modify object code as it is both very difficult and therefore risky.

In the early days of computing it was normal for system vendors to provide source code and the object code together. For example, IBM shipped the source code of their mainframe operating systems. Later, software vendors started holding back source code, and released only object code. This "closed source" approach dominated the software product industry for some time.

Copyright and Copyleft

As software vendors were embracing the closed source approach, Richard Stallman started the GNU project with the aim of building an operating system whose source code was freely available. A few years later the GNU project evolved into the Free Software Foundation (FSF). In order to preserve the value of GNU work, Stallman came up with the idea of the "copyleft".

Copyleft is an extension of copyright achieved through a license. The license devised by the FSF to realize copyleft is the GPL, the GNU Public License.

The objective of the GPL is to ensure that work made available can be freely distributed and changed, but cannot be wrapped and hidden inside a closed source product. As Stallman puts it: "The central idea of copyleft is that we give everyone permission to run the program, copy the program, modify the program, and distribute modified versions--but not permission to add restrictions of their own.".

Open or Free

The Free Software Foundation talks of "Free" software. The use of the word free, however, has caused some confusion and blurring of the intended message. Some people took free to refer to money, rather than liberty.

An alternative to the GPL came from the University of California at Berkeley, who made available the Berkeley Source Distribution (BSD). BSD is a complete operating system environment derived from the AT&T operating system, UNIX. BSD was made available under a license called the BSD License.

The FSF maintained that the BSD License did not guarantee that software would remain free. They have a point. For example, Microsoft use the BSD IP stack in many of their operating systems, but have not released the source code for it, because under the BSD license, they don't have to. Had the IP stack been released under the GPL, they would.

The number of licenses which permit sharing of source code continued to increase, much to the irritation of the Free Software Foundation who felt that everyone should use the GPL. The quality of argument put forward by the FSF was often obscured by the confrontational tenor of delivery.

The term "open source" came from a group of people who wanted an end to the confrontation. This group formed the Open Source Initiative (OSI). The OSI maintain a list of licenses which meet their open source definition.

Needless to say, the FSF feel that OSI are softening the protection for free software. The OSI, on the other hand, feel that theirs is a pragmatic realization of the spirit of free software.

Today, there is still a tension between the FSF and the OSI. This is a healthy situation which has no impact on day-to-day development project issuses, but keeps the debate alive and fresh. Both the FSF and the OSI are a great source of information for those wishing to understand more about free / open source software.

Further Reading

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