Fork (software Development) - Forking Free and Open Source Software

Forking Free and Open Source Software

Free and open source software may be legally forked without the approval of those currently managing a software project or distributing the software, per the definitions of "free software and "open source"":

• "Freedom 3: The freedom to improve the program, and release your improvements to the public, so that the whole community benefits"
• "3. Derived Works: Redistribution of modifications must be allowed, to allow legal sharing and to permit new features or repairs".

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.

Eric S. Raymond, in his essay Homesteading the Noosphere, 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:

Forking is considered a Bad Thing—not merely because it implies a lot of wasted effort in the future, but because forks tend to be accompanied by a great deal of strife and acrimony between the successor groups over issues of legitimacy, succession, and design direction. There is serious social pressure against forking. As a result, major forks (such as the Gnu-Emacs/XEmacs split, the fissioning of the 386BSD group into three daughter projects, and the short-lived GCC/EGCS split) are rare enough that they are remembered individually in hacker folklore.

David A. Wheeler notes four possible outcomes of a fork, with examples:

1. 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.
2. A re-merging of the fork (e.g., egcs becoming "blessed" as the new version of gcc).
3. The death of the original (e.g. the X.Org Server succeeding and XFree86 dying).
4. Successful branching, typically with differentiation (e.g., OpenBSD and NetBSD).

More recently, distributed revision control (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 branch the repository, and later seek to have your changes integrated with the main repository. Sites such as Github, Bitbucket and Launchpad 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.

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 of the original project, e.g. MariaDB for MySQL or LibreOffice for OpenOffice.org.