"If I have seen farther than others, it is because I have stood on the shoulders of giants." - Sir Isaac Newton

"Open Source" is how we describe any form of creativity for which its authors have chosen to share the methodology or "recipe" of their creation with the world. Sometimes authors prefer to hide the recipe from view, usually in effort to maximise their return from this exclusive knowledge - this is the opposite of open source: proprietary knowledge. In the case of software, the "recipe" takes the form of source code, or the logical text written by a programmer that a computer interprets to create a software application that is useful to an end user.

Open source is a difficult concept for many, especially in a commercial world where non-disclosure agreements and carefully safe-guarded intelletctual property policies are the norm rather than the exception. Most of the world's most heavily marketed desktop software applications come from this restrictive proprietary world.

"Closed Source" or proprietary software is characterised by easy-to-misplace software "activation keys", product registration, "End User License Agreements" (go ahead and read this one), "seat-license" restrictions, "Software Assurance", and visits from the Business Software Alliance (BSA). The purpose of these protection mechanisms is ostensibly to minimise software 'piracy', but the reality is that it doesn't have any effect whatsoever on piracy and really an attempt to maximise revenue by restricting how people use the software.

These proprietary licenses create in an unfamiliar situation for consumers who have a certain expectation of what it means to "own" something. Unlike, say, a book, which you could read at home, or on the bus, or during your lunch break at work - and loan to someone else when you're done with it - many proprietary licenses place strict and seemingly arbitrary limitations on how the user can make use of it, e.g. by requiring users to purchase two copies, one for home and one for work, or prohibiting the resale of the software. In effect, closed source licenses have one purpose: to take away your freedom to share or change the software you have purchased in order to maximise the revenue of the software provider. In fact, in most cases, closed source licenses stipulate that you don't even own the software itself, only the right to use it under the manufacturer's very restrictive terms.

In stark contrast, open source software is characterised by enforced perpetual freedom of use. There are a handful of licenses used by the open source community to protect the open nature of its work which fall into two main groups.

The first group says that source code released under this license can be used, changed or incorporated by anyone in any way, with the one condition being that the original copyright notice is retained in the code. The best known example of this type of license is the BSD license. BSD stands for Berkeley Software Design, Inc., a group at Berkeley University in California, USA, who developed a one of the most successful versions of the Unix operating system, known as BSD Unix. Well known open source software released under the BSD license include implementations of FTP and Telnet as well as the well known Sendmail MTA, the Apache webserver, and the BIND DNS server. The BSD license is usually used for infrastructural software that implements a standard - it is released under this license so as not to provide a disincentive for closed source software developers to adopt it. It does, however, mean that software written by volunteers and then made freely available can be downloaded and packaged by a closed source software company and then resold in binary form (i.e. without the source code) even back to the original author. The company doesn't have to provide any further compensation to the original author so long as their copyright is buried amongst the 1s and 0s in the binary executable. A case in point: a string search of Microsoft's Telnet and FTP binaries, fixtures of Windows since the early days, reveals frequent references to "Regents of Berkeley" (part of BSD's copyright notice). These two programs have been immensely profitable for Microsoft as they provide critical networking capabilities for the Windows platform which which they are bundled, but Microsoft have not provided any compensation to the original developers whatsoever, nor have they even publically acknowledged their "borrowing" of and profitting from the BSD group's pioneering and generously licensed work.

For some people, however, chief among them Richard M. Stallman of the Free Software Foundation and GNU fame, the idea of a company profiting from software written in the spirit of generosity and freedom and given to the greater community without giving so much as a "thanks very much" is unacceptable. And fair enough, too. We all learn as children that it is right to "share and share alike." If you profit from the work of others, good ethics require that you give credit where it is due, and at least a portion of those profits to those who made your success possible. Anything less is tantamount to theft, and at the very least, very poor form. Even more important, though, is the concept of freedom. The idea is that an author who makes his or her work freely available in the form of source code should always have access to the source code of any other work which is derived from that original work. What starts free should remain free. To codify this concept, Richard M. Stallman (a.k.a. RMS) wrote the remarkable GNU General Public License, which is applied to a work by declaring it "copyleft" and it forms the cornerstone of the open source movement. The copyleft is simply a general method of making any instance of creative endeavour impossible to copyright. According to the definitive GNU site:

Copyleft is a general method for making a program free software and requiring all modified and extended versions of the program to be free software as well.

RMS quite pointedly refers to any software licensed under the GPL as "free software" rather than "open source" because, for him the key to the GPL is freedom. Unfortunately, in the English language, "free" can mean both freedom and zero cost, and this ambiguity has been something of a marketing debacle for the more widespread acceptance, especially among the business world, of GPL software. The adage "you get what you pay for" has been difficult to dispell for the uninitiated. To improve its marketing potential, and to empower the movement by coining a new name, a group of hacking luminaries, headed by Bruce Perens and Eric S. Raymond (alias ESR, author of the hugely influential Cathedral and Bazaar essay) decided, in a stroke of rebranding genius, to call this re-emerging collaborative software development phenomenon "open source" software.

Way back in 1992, Linus Torvalds, the originator of Linux, demonstrated (accidently, according to him) great foresight by chosing to release his fledgeling Linux operating system under the GPL license. Contrary to expectations, Linux has thrived under the auspices of the GPL, and now enjoys the support of a huge and growing cadre of individuals, corporations, institutions, and governments worldwide because it provides security against the domination of information technology by any one entity for its own profit at the expense of everyone else. The only dissenting voices belong to those who feel disadvantaged by the GPL and related licenses - those who cannot profit from incorporating GPL software into their products without also making the source code for that software available. Microsoft, the convicted monopolist supplier of commodity software and operating systems and famed for running roughshod over any company it considers competitive or uncooperative, has been thwarted with every attempt to destroy the open source movement. Because it cannot freely incorporate any of Linux's many innovations as it did with BSD licensed software, it has publicly declared the GPL "a cancer," bad for business, an "intellectual property destroyer", and, most absurdly, "unamerican"...

It would appear, according to Microsoft's Jim Allchin at least, that it's unamerican be principled with one's generosity: to make the fruits of one's own creativity and hard work available for posterity and expect that work to remain free. This is a very threatening prospect for companies like Microsoft who can only retain their dominant market positions by usurping completely, claiming both profits and credit, the work of real innovators by any means possible. Pretty unfair and unreasonable of the open source community, don't you think?

It is important to note that the GPL does not in any way proclude entities from charging good money for GPL software or derivatives thereof, it simply stipulates that the source code - not the same thing as software, which is usually distributed in binary form - must be made available on request if the software in question is being distributed. If, on the other hand, the software is only being used in-house, no such requirement applies.

For those readers who are also familiar with software development, the reality of the GPL is somewhat restrictive. Technically, if you write software which, for example, calls or links to a precompiled library carrying a GPL license, your software is also GPL... This poses serious problems for proprietary software developers who want to release their software for the Linux platform as they would have to link to GPL'd libraries - all programs that run on Linux link to the basic Glibc "C" libraries which implement nearly all of the basic low-level functionality required by any software program (The "g" in GLibc stands for GNU as in the GNU "C" Compiler - written, originally, by RMS himself - which is used to compile nearly every executable on a Linux system). This domino effect would have put a serious crimp in Linus' plans for world domination. Luckily for us, RMS is not an unreasonable man (uncompromising, yes, but we wouldn't have him any other way!), and he sat down and developed the LGPL or Lesser GPL, as a special license for libraries and related software constructs which, though free themselves, don't force applications which use them less directly (i.e. link to them) to change their own license conditions. The GLibc and most other shared libraries on Linux are licensed under the terms of the LGPL for that reason.

Anyone wanting to read a fascinating debate on licenses, should look at this by Tim O'Reilly.

[Suggestions on improvements to this document are always welcome...]