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In
software engineering
Software engineering is a systematic engineering approach to software development.
A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term '' ...
, a project fork happens when developers take a copy of
source code
In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the wo ...
from one
software package
Software package may refer to:
* Package (package management system), in which individual files or resources are packed together as a software collection that provides certain functionality as part of a larger system
* Software suite, which provid ...
and start independent development on it, creating a distinct and separate piece of software. The term often implies not merely a
development branch Branching, in version control and software configuration management, is the duplication of an object under version control (such as a source code file or a directory tree). Each object can thereafter be modified separately and in parallel so that th ...
, but also a split in the developer community; as such, it is a form of
schism
A schism ( , , or, less commonly, ) is a division between people, usually belonging to an organization, movement, or religious denomination. The word is most frequently applied to a split in what had previously been a single religious body, suc ...
. Grounds for forking are varying user preferences and stagnated or discontinued development of the original software.
Free and open-source software
Free and open-source software (FOSS) is a term used to refer to groups of software consisting of both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the source ...
is that which, by definition, may be forked from the original development team without prior permission, and without violating
copyright
A copyright is a type of intellectual property that gives its owner the exclusive right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, education ...
law. However, licensed forks of proprietary software (''e.g.''
Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
) also happen.
Etymology
The word "fork" has been used to mean "to divide in branches, go separate ways" as early as the 14th century. In the software environment, the word evokes the
fork system call, which causes a running process to split itself into two (almost) identical copies that (typically) diverge to perform different tasks.
In the context of software development, "fork" was used in the sense of creating a revision control "
branch
A branch, sometimes called a ramus in botany, is a woody structural member connected to the central trunk (botany), trunk of a tree (or sometimes a shrub). Large branches are known as boughs and small branches are known as twigs. The term '' ...
" by
Eric Allman as early as 1980, in the context of
SCCS:
The term was in use on
Usenet
Usenet () is a worldwide distributed discussion system available on computers. It was developed from the general-purpose Unix-to-Unix Copy (UUCP) dial-up network architecture. Tom Truscott and Jim Ellis conceived the idea in 1979, and it was ...
by 1983 for the process of creating a subgroup to move topics of discussion to.
"Fork" is not known to have been used in the sense of a community schism during the origins of Lucid Emacs (now
XEmacs) (1991) or the
BSDs (1993–1994);
Russ Nelson used the term "shattering" for this sort of fork in 1993, attributing it to
John Gilmore John Gilmore may refer to:
* John Gilmore (activist) (born 1955), co-founder of the Electronic Frontier Foundation and Cygnus Solutions
* John Gilmore (musician) (1931–1995), American jazz saxophonist
* John Gilmore (representative) (1780–1845), ...
. However, "fork" was in use in the present sense by 1995 to describe the XEmacs split, and was an understood usage in the
GNU Project by 1996.
Forking of free and open-source software
Free and
open-source software
Open-source software (OSS) is computer software that is released under a license in which the copyright holder grants users the rights to use, study, change, and distribute the software and its source code to anyone and for any purpose. Op ...
may be legally forked without prior approval of those currently developing, managing, or distributing the software per both
The Free Software Definition
The Free Software Definition written by Richard Stallman and published by the Free Software Foundation (FSF), defines free software as being software that ensures that the end users have freedom in using, studying, sharing and modifying that softwa ...
and
The Open Source Definition
''The Open Source Definition'' is a document published by the Open Source Initiative, to determine whether a software license can be labeled with the open-source certification mark.
The definition was taken from the exact text of the Debian Free ...
:
[
In free software, forks often result from a schism over different goals or personality clashes. In a fork, both parties assume nearly identical code bases, but typically only the larger group, or whoever controls the Web site, will retain the full original name and the associated user community. Thus, there is a reputation penalty associated with forking.][ The relationship between the different teams can be cordial or very bitter. On the other hand, a ''friendly fork'' or a ''soft fork'' is a fork that does not intend to compete, but wants to eventually merge with the original.
]Eric S. Raymond
Eric Steven Raymond (born December 4, 1957), often referred to as ESR, is an American software developer, open-source software advocate, and author of the 1997 essay and 1999 book ''The Cathedral and the Bazaar''. He wrote a guidebook for the ...
, in his essay ''Homesteading the Noosphere "Homesteading the Noosphere" (abbreviated HtN) is an essay written by Eric S. Raymond about the social workings of open-source software development. It follows his previous piece "The Cathedral and the Bazaar" (1997).
The essay examines issues of p ...
'', stated that "The most important characteristic of a fork is that it spawns competing projects that cannot later exchange code, splitting the potential developer community". He notes in the Jargon File
The Jargon File is a glossary and usage dictionary of slang used by computer programmers. The original Jargon File was a collection of terms from technical cultures such as the MIT AI Lab, the Stanford AI Lab (SAIL) and others of the old ARPANET A ...
:
David A. Wheeler notes[Why Open Source Software / Free Software (OSS/FS, FLOSS, or FOSS)? Look at the Numbers!: Forking]
(David A. Wheeler) four possible outcomes of a fork, with examples:
# The death of the fork. This is by far the most common case. It is easy to declare a fork, but considerable effort to continue independent development and support.
# A re-merging of the fork (''e.g.'', egcs
The GNU Compiler Collection (GCC) is an optimizing compiler produced by the GNU Project supporting various programming languages, hardware architectures and operating systems. The Free Software Foundation (FSF) distributes GCC as free software ...
becoming "blessed" as the new version of gcc.)
# The death of the original (''e.g.'' the X.Org Server
X.Org Server is the free and open-source implementation of the X Window System display server stewarded by the X.Org Foundation.
Implementations of the client-side X Window System protocol exist in the form of ''X11 libraries'', which serve a ...
succeeding and XFree86 dying.)
# Successful branching, typically with differentiation (''e.g.'', OpenBSD
OpenBSD is a security-focused, free and open-source, Unix-like operating system based on the Berkeley Software Distribution (BSD). Theo de Raadt created OpenBSD in 1995 by forking NetBSD 1.0. According to the website, the OpenBSD project em ...
and NetBSD
NetBSD is a free and open-source Unix operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is a ...
.)
Distributed revision control
In software development, distributed version control (also known as distributed revision control) is a form of version control in which the complete codebase, including its full history, is mirrored on every developer's computer. Compared to centra ...
(DVCS) tools have popularised a less emotive use of the term "fork", blurring the distinction with "branch". With a DVCS such as Mercurial or Git, the normal way to contribute to a project, is to first create a personal branch of the repository, independent of the main repository, and later seek to have your changes integrated with it. Sites such as GitHub
GitHub, Inc. () is an Internet hosting service for software development and version control using Git. It provides the distributed version control of Git plus access control, bug tracking, software feature requests, task management, continuous ...
, Bitbucket and Launchpad
A launch pad is an above-ground platform from which rocket- missiles or space launch vehicles take off vertically.
Launch pad may also refer to:
Computing
* Launchpad (macOS), an application launcher introduced in Mac OS X Lion
* Launch Pad (s ...
provide free DVCS hosting expressly supporting independent branches, such that the technical, social and financial barriers to forking a source code repository are massively reduced, and GitHub uses "fork" as its term for this method of contribution to a project.
Forks often restart version numbering from 0.1 or 1.0 even if the original software was at version 3.0, 4.0, or 5.0. An exception is when the forked software is designed to be a drop-in replacement for the original project, ''e.g.'' MariaDB for MySQL
MySQL () is an open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A relational database o ...
or LibreOffice for OpenOffice.org.
The BSD licenses
BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lice ...
permit forks to become proprietary software, and copyleft
Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose, ...
proponents say that commercial incentives thus make proprietisation almost inevitable. (Copyleft licenses can, however, be circumvented via dual-licensing with a proprietary grant in the form of a Contributor License Agreement.) Examples include macOS
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...
(based on the proprietary NeXTSTEP
NeXTSTEP is a discontinued object-oriented, multitasking operating system based on the Mach kernel and the UNIX-derived BSD. It was developed by NeXT Computer in the late 1980s and early 1990s and was initially used for its range of proprieta ...
and the open source FreeBSD
FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...
), Cedega and CrossOver
Crossover may refer to:
Entertainment
Albums and songs
* ''Cross Over'' (Dan Peek album)
* ''Crossover'' (Dirty Rotten Imbeciles album), 1987
* ''Crossover'' (Intrigue album)
* ''Crossover'' (Hitomi Shimatani album)
* ''Crossover'' (Yoshino ...
(proprietary forks of Wine
Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are m ...
, though CrossOver tracks Wine and contributes considerably), EnterpriseDB (a fork of PostgreSQL
PostgreSQL (, ), also known as Postgres, is a free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. It was originally named POSTGRES, referring to its origins as a successor to the In ...
, adding Oracle compatibility features), Supported PostgreSQL with their proprietary ESM storage system, and Netezza'sNetezza
proprietary highly scalable derivative of PostgreSQL. Some of these vendors contribute back changes to the community project, while some keep their changes as their own competitive advantages.
Forking proprietary software
In proprietary software
Proprietary software is software that is deemed within the free and open-source software to be non-free because its creator, publisher, or other rightsholder or rightsholder partner exercises a legal monopoly afforded by modern copyright and int ...
, the copyright is usually held by the employing entity, not by the individual software developers. Proprietary code is thus more commonly forked when the owner needs to develop two or more versions, such as a windowed version and a command line version, or versions for differing operating systems, such as a word processor
A word processor (WP) is a device or computer program that provides for input, editing, formatting, and output of text, often with some additional features.
Word processor (electronic device), Early word processors were stand-alone devices ded ...
for IBM PC
The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
compatible machines and Macintosh
The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc., Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and ...
computers. Generally, such internal forks will concentrate on having the same look, feel, data format, and behavior between platforms so that a user familiar with one can also be productive or share documents generated on the other. This is almost always an economic decision to generate a greater market share
Market share is the percentage of the total revenue or sales in a market that a company's business makes up. For example, if there are 50,000 units sold per year in a given industry, a company whose sales were 5,000 of those units would have a ...
and thus pay back the associated extra development costs created by the fork.
A notable proprietary fork not of this kind is the many varieties of proprietary Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
—almost all derived from AT&T Unix under license and all called "Unix", but increasingly mutually incompatible.[Fear of forking]
– An essay about forking in free software
Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...
projects, by Rick Moen ''See'' UNIX wars
The Unix wars were struggles between vendors to set a standard for the Unix operating system in the late 1980s and early 1990s.
Origins
Although AT&T Corporation created Unix, by the 1980s, the University of California, Berkeley Computer Syste ...
.
See also
* List of software forks
This is a list of notable software forks.
Undated
*The many varieties of proprietary Unix in the 1980s and 1990s — almost all derived from AT&T Unix under licence and all called "Unix", but increasingly mutually incompatible. ''See'' UNIX war ...
* Source port
* Downstream (software development)
In software development, downstream refers to a direction away from the original authors or maintainers of software that is distributed as source code, and is a qualification of a patch. For example, a patch ''sent downstream'' is offered to the ...
* Group decision-making Group decision-making (also known as collaborative decision-making or collective decision-making) is a situation faced when individuals collectively make a choice from the alternatives before them. The decision is then no longer attributable to an ...
* Modular programming
** Modding
''Modding'' is a slang expression derived from the English verb " to modify". The term refers to modification of hardware, software, or anything else, to perform a function not originally intended by the designer, or to achieve bespoke specific ...
* Custom software
* Personalization
Personalization (broadly known as customization) consists of tailoring a service or a product to accommodate specific individuals, sometimes tied to groups or segments of individuals. A wide variety of organizations use personalization to improv ...
* Team effectiveness
Team effectiveness (also referred to as group effectiveness) is the capacity a team has to accomplish the goals or objectives administered by an authorized personnel or the organization. A team is a collection of individuals who are interdependen ...
** Duplicate code
* ROM Hacking
References
External links
Right to Fork
at Meatball Wiki
MeatballWiki is a wiki dedicated to online communities, network culture, and hypermedia. According to founder Sunir Shah, it ran on "a hacked-up version of UseModWiki". In April 2013, after several spam attacks and a period of downtime, the site ...
* A PhD examining forking
(Nyman, 2015)
"Understanding Code Forking in Open Source Software – An examination of code forking, its effect on open source software, and how it is viewed and practiced by developers"
{{DEFAULTSORT:Fork (Software Development)
Software project management