An open source software is a software that has a licence granting the software's user several rights that traditional software licences do not. The idea of free access to a software's source code isn't new, as it has existed as long as there's been computer software. However, open source as a term has gotten more meanings and it's relevance in business has changed.
The evolution of open source can be divided into three phases:
During the first phase the idea of free software was created. It emphasises the 1985 founded Free Software Foundation's (FSF) ideal of freedom in software developing and usage. FSF aims to change software business so that it secures the basic freedoms FSF has defined. The GPL-licence, created by FSF, is essential tool for reaching this goal.
In the second phase the term open source was coined. In it the ethical principles of freedom were moved aside and companies, decentralized software developing process and open collaboration of software developers were brought to the spotlight. At this time, in 1998, the Open Source Initiative (OSI) was founded. It approved open source licences and maintained a list of them, getting the extensive support of software business. It also provided a base for growing community of developers.
in the third phase, commercial open source, it's typical to use open source as a part of traditionally licenced commercial products, services and trusted business models of this field. The objective of using open source is especially to lower the costs and increase the developing speed. Typical phenomena are the mixed source -products using both open and closed source technologies together and offering software as a service (this idea is also known by it's acronym SaaS). The third phase begun in 2005.
Source code is the blueprint of a computer software. In it, the programmers write the commands and directions that make the computer work the way they want. For the computer to understand these commands, the source code must usually be translated to so called executable form before it's run.
Software's translated, executable form is not interpreted by humans. Because closed software source codes are usually treated as trade secrets and no editing or distribution rights are given, those who buy the software have no technical or juducial means or rights to research the software or make any changes to it. Open source software and it's licence enable all this either for the buyer of the software or any other third party.
Few user or company think they need the source, as they are purchasing software products, not the actual code. There can however be a big difference between buying a closed or open source product. The most important advantage with the open source is independence from the software producer. When the product includes the source code and a right to use it for making changes to the software, buyer can minimize the risk of being dependent to just one software producer, as additional developement, maintenance and other possible work may be done by someone else than the original developer.
It's also good to realize, that some critical systems requiring special transparency may have to be checked by the buyer beforehand. When it comes to computer software, the only way to make this possible is the open source.
Open source software doesn't have a standard definition and open source isn't a judicial term. As noted above, the terms free software and open source were created in the 80's by Free Foundation Software and in 1998 by Open Source Initiative, respectively.
From the public administration's viewpoint these concepts have no essential difference and they both include the same basic freedoms concerning usage, copying, editing and distribution. The OSI-definition is the most used in business world, eg. JIT 2007 -clauses refers to it while defining open source.
Open Source Initiative's definition states that open source software must comply with the following criteria:
1. Free Redistribution The license shall not restrict any party from selling or giving away the software as a component of an aggregate software distribution containing programs from several different sources. The license shall not require a royalty or other fee for such sale.
2. Source Code The program must include source code, and must allow distribution in source code as well as compiled form. Where some form of a product is not distributed with source code, there must be a well-publicized means of obtaining the source code for no more than a reasonable reproduction cost preferably, downloading via the Internet without charge. The source code must be the preferred form in which a programmer would modify the program. Deliberately obfuscated source code is not allowed. Intermediate forms such as the output of a preprocessor or translator are not allowed.
3. Derived Works The license must allow modifications and derived works, and must allow them to be distributed under the same terms as the license of the original software.
4. Integrity of The Author's Source Code The license may restrict source-code from being distributed in modified form only if the license allows the distribution of "patch files" with the source code for the purpose of modifying the program at build time. The license must explicitly permit distribution of software built from modified source code. The license may require derived works to carry a different name or version number from the original software.
5. No Discrimination Against Persons or Groups The license must not discriminate against any person or group of persons.
6. No Discrimination Against Fields of Endeavor The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research.
7. Distribution of License The rights attached to the program must apply to all to whom the program is redistributed without the need for execution of an additional license by those parties.
8. License Must Not Be Specific to a Product The rights attached to the program must not depend on the program's being part of a particular software distribution. If the program is extracted from that distribution and used or distributed within the terms of the program's license, all parties to whom the program is redistributed should have the same rights as those that are granted in conjunction with the original software distribution.
9. License Must Not Restrict Other Software The license must not place restrictions on other software that is distributed along with the licensed software. For example, the license must not insist that all other programs distributed on the same medium must be open-source software.
10. License Must Be Technology-Neutral No provision of the license may be predicated on any individual technology or style of interface.