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What is OpenSource?

OpenSource is software where the source code is open to the public. The source code, or simly the source, consists of the instructions that are written by the developers in a programming language of their choice. These files, the source files, are not runable on the computer, they contain program instructions in plain text.
To make an executable file from these source files we need a compiler. A compiler is a programm that translates the program instructions in plain text to machine code, the language that the processor understands directly. These machine instructions are assembeled in a file that can be executed by the computer, the binary program.
Source Code - Compiler - Binary Program
In opposite to OpenSource these source codes are not open to the user in the most cases. The producers keep them a secret with copyright, only the binary program is delivered to the users. Hence it is called proprietary software.
OpenSource is going consequently the other way, the source code is free and open to the user, for reading as well as modifying and testing.


History of the OpenSource Model

The beginning of the OpenSource model took place in 1983 and was caused by Richard Stallman, a member of MIT (Massachusets Institute of Technology). Unix was widely used in the universities and the source code was free and open. When the company AT&T restricted the free usage of the source codes Richard Stallman created the GNU (GNU is Not Unix) project and founded the Free Software Foundation. The goal was to program a free unix-like operating system. Free in this case means that it should be obtainable without cost and the source codes should be open.
The Free Software Foundation decoyed a lot of programmers in a short time and lots of tools and programs were made. These were built after the original Unix tools, but later they got more powerful and more stable then the originals.
In the year 1991 Linus Torvalds entered the scene and began to program an own operating system kernel. He published his work in the internet and soon he found many supporters and interested workers. This cooperation released a working operating system kernel in 1992. As before here the motivation arised from dissatisfaction about the commercial products and the high cost to purchase a commercial operating system.
Originally the term Linux only denominates the operating system kernel. Later on this item included the utilities and application programs which were and are developed in the internet community as OpenSource. Until the year 1996 more then one million developers contributed to the success of Linux and OpenSource.


Copyright - Copyleft

To confront the item of Copyright with Copyleft is a wordplay by Richard Stallman. In contrast to Copyright licenses the Copyleft license requires that an OpenSource software after modification and new release has to be left under this license. This assures that further developing of OpenSource software cannot become a proprietary product, that means the source codes may not become the secret of a producer.

The most important licenses in the domain of OpenSource are

GNU General Public License - GPL

The GPL gives every user the right to copy and distribute the source code. All copies have to contain a disclaimer and a copy of the GPL.
The user is also allowed to modify and enlarge the source code and to distribute copies under the condition that he documents his modifications.
The source code has to be delivered with the product or to be available publicly.
The distributor is allowed explicitely to take fees for the effort of making copies and demand payment for warranty and support to the customer.

GNU Lesser General Public License - LGPL

The LGPL was originally named GNU Library General Public License, what directly shows the meaning of this license. This license covers special features of library programs. In main parts it is identical to the GPL, for libraries the following extensions are made:
A user, who distributes or developes further, has to care that it remains a working library.
The new developement has to stay under the LGPL or may be published under the GPL.
Proprietary software may use OpenSource libraries,

GNU Free Documentation License - GFDL

The GFDL describes the conditions for documentation for OpenSource software.
Here, too, the free usage and distribution of copies is granted, even in printed form. As this is a Copyleft license the redistribution has to underlie the GFDL. A special value is given to the fact of tranparency, that means, that electronic copies should be delivered in file formats that are easy to be changed. The same should be apllied to pictures, simple picture processing software shall be able to handle images in OpenSource documents. New modifications and distributions have to keep a history of the developement of the document as well as of all authors contributed to a document. An author can demand that on the outside of the package of a printed document a covertext is applied.

BSD - Berkeley Software Distribution

The license of the Berkeley Software Distribution is a "Non-Copyleft" license. Modifications and further developing of the software is granted, but the result of further developement has not to be published under the same license. In the case of the BSD license it is possible and happened already, to change free software to a proprietory product.

A list of other licenses can be found at the Free Software Foundation and on the pages of OpenSource.org.

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