Open Source Software,

Open Source Software, form of software in which users are given or can obtain the original source code from which a computer program is compiled, and which also includes a license allowing users to use, modify, and redistribute the code. Users can then review the software, add features to it or hire programmers to add features, or fix errors known as bugs, rather than wait for the original software publisher or creator to release a “patch” or bring out a new version. With open source software, programmers—many of them nonprofessionals—contribute to the computing community by making their improvements and bug fixes available to other users.

This type of peer review is open to community input, standards, and verification, and is thought to lead to more reliable software. It is also thought to speed up the software development process. In some cases, the peer review may be uninfluenced by deadlines or other commercial concerns. However, as open source software development has evolved, companies such as the International Business Machines Corporation (IBM), Sun Microsystems, Inc., and others have offered an increasing number of open source products.

The mere fact of making source code available does not make a program “open source,” according to the definition of open source provided by the Open Source Initiative, a nonprofit corporation. The organization’s formal definition specifies that, among other things, anyone has the right to modify and redistribute program code and derived works. The OSI definition of “open source” is roughly the same as the definition of “free software” advanced by the Free Software Foundation (FSF), founded by United States computer programmer Richard Stallman and embodied in the FSF’s General Public License (GPL). Stallman started the free software movement in 1983 when he announced plans to write a complete UNIX-compatible software system called GNU (which stands for GNU’s Not UNIX) and to give it away for free. Ultimately, this led to the creation of the GNU/Linux and GNU/Hurd operating systems.

The Open Source Initiative group distanced itself from the Free Software Foundation in 1998 when it adopted the open source label, arguing that “open source” carried less ideological baggage than “free software.” The group believed the phrase “open source” would have greater appeal to businesses, even though the software and the open approach were roughly the same as that put forward by the Free Software Foundation. Since 1998, the two movements have generally shifted in philosophy. The Open Source Initiative tends to view itself as a software development-related initiative; the Free Software Foundation views itself as a social movement.

The GNU/Linux operating system, usually called Linux, is the most successful and well-known example of open source software. Linux is a UNIX-like operating system that many use as an alternative to commercial UNIX or Windows operating systems. Finnish-born software engineer Linus Torvalds used GNU C—an open source version of the C programming language—to write the Linux operating system kernel and released it under the Free Software Foundation’s GPL, although it was not written as an FSF project.

As of 2003 Linux had made its greatest inroad as operating system software for servers. Several companies, including IBM and Sun, promoted Linux to compete with various exclusive versions of UNIX and with server software developed by Microsoft Corporation. (Encarta Encyclopedia is published by Microsoft.) In June 2003 a widely distributed memo written by Microsoft chief executive officer Steve Ballmer acknowledged that Linux was a growing threat to Microsoft’s business. The memo said that an estimated 500,000 of the approximately 1 million UNIX-operated servers in the United States were considered candidates for migration to Linux. Linux was also being adopted in some businesses and government offices where personal computers (PCs) were networked. According to the publication LinuxWorld, there were 18 million users of Linux in 2003, twice the number estimated in 1998. Many analysts, however, doubted that Linux would achieve popularity as a desktop operating system.

In addition to the Linux operating system, the Apache open source program, which is designed for Web servers, including those running the UNIX and Windows NT operating systems, has been the most popular Web server on the Internet since 1996. According to a 2003 Netcraft Web Server Survey, about 64 percent of Web sites on the Internet were using Apache.