BSD and GPL licensing

Two of the most common free software licenses are the BSD and GPL licenses. There has been continuing discussion over the relative merits of the use of either license in free software projects.

The BSD license essentially allows the user of source code released under this license to be free to do whatever that user wishes to do with the code, with very few restrictions. This means that code released under this license can be used in both open source and closed source situations. Proponents of copyleft-style software licenses such as the GPL argue that the non-copyleft nature of the BSD license becomes detrimental to open source in general, as it does not expressly require that users who extend BSD-licensed software must openly release their modifications. However, it is counter-argued that the non-copyleft nature of the BSD license encourages inclusion of well-developed standard code into closed source projects, and it is further argued that licenses such as the GPL discourages this, forcing people who wish to develop closed source projects to reinvent the wheel to maintain their ability to keep the project closed source, doing it in possibly a less-efficient way than the open source version does it (as it has been open to more scrutiny and patching).

However, the BSD license allows commercial organizations to build upon the inventions of free software and research environments that use free software licenses to further develop their programs. A recent and successful example of this is the Mac OS X operating system, based on parts of the BSD code.

Those who advocate the use of copyleft licenses such as the GPL argue that the requirement that software licensed under the GPL allows the freedom to copy, use, study, modify, and distribute the source code, with the advantage that other improvements to GPL-licensed software are ensured with its requirement that the extensions to the software be freely available as well. However, it is said by some that the requirement that the source code be also freely available does not give the user "freedom" to make closed source software under such a license, though this "freedom" is not one of four freedoms of Free software as outlined by the Free Software Foundation, who also holds that denying others their freedom by witholding source code from them is not a "freedom", rather an form of power (http://www.gnu.org/philosophy/freedom-or-power.html). GPL supporters often point out that since BSD licensed code allows distribution of closed source modified versions, that the work of the contributor has been "stolen", and as such is not fair and therefore no code should be licensed under BSD-style licenses - however, the original free, BSD licensed code is still available for all to use and improve, with the copyrights still remaining to the author.

Traditionally, Linux associated software is licensed under the GPL, whilst BSD derivatives often use the BSD license. Code licensed under the BSD license can be relicensed under the GPL (the BSD license is said to be "GPL-compatible") without securing the consent of all original authors; but code under the GPL cannot be relicensed under the BSD license without securing the consent of all original authors, as the BSD license does not necessarily require the source code to be again freely available.

The advertising clause

The original BSD license contains a clause requiring acknowledgments to appear in all advertising materials mentioning the software (see BSD license). The GNU project calls this clause "obnoxious", as well as pointing out that it makes the license incompatible with the GPL because it adds a requirement not present in the GPL. Since then, the clause was officially removed from the original BSD distribution, and other BSD distributions followed suit, but NetBSD still uses the original version of the license.

External links

• Freedom or Power? (http://www.gnu.org/philosophy/freedom-or-power.html) (Free Software Foundation) — describing "freedom" as freedom for all instead of one

• The BSD License Problem (http://www.gnu.org/philosophy/bsd.html) (Free Software Foundation) — advocacy against the advertising clause