BSD and GPL licensing

From Free net encyclopedia

Two of the most common free software licenses are the BSD and GPL licenses. Whereas software released with both these licenses is free, they differ substantially in the way the source code can be used. The merits and shortcomings of either license in free software projects is a common cause of flame wars.

Image:BSD-daemon-rendering.png Many users and developers of BSD-based operating systems have a different position on licensing. The main difference is the belief that the copyleft licenses, particularly the GNU General Public License (GPL), are too complicated and have restrictions which are undesirable. The GPL, instead, requires derivative work to be released according to the GPL, in what is termed a "viral" effect of copyleft licenses. Essentially, the BSD license's only requirement is to acknowledge the original authors, and poses no restrictions on how the source code may be used. As a result, BSD code can find its way into proprietary software that only acknowledge the source (See OpenSSH, for example). For instance, the IP stack in Microsoft Windows and Mac OS X are derived from BSD-licensed software.

Image:Heckert GNU white.svg GPL supporters claim that mandating derivative works remain free fosters the growth of free software and requires equal participation by all users. Developers who use GPL code have to share their improvements with the community, supporting the growth of the software they received.

Supporters of the BSD license argue that it is more free than the GPL because it grants the right to do anything with the source code, second only to software in the public domain. The nature of BSD has encouraged the inclusion of well-developed standard code into proprietary software. In response, GPL supporters claim that this is more a form of power than a freedom.[1] The right to make closed-source code is therefore not included in the Free Software Foundation's "four freedoms of free software"; using, studying, copying, and distributing modifications of the code.

Existing free software BSDs tend to avoid including software licensed under the GPL in the core operating system, or the base system, except as a last resort when alternatives are non-existent or vastly less capable, such as with GCC. The OpenBSD project has acted to remove GPL-licensed tools in favour of BSD-licensed alternatives, some newly written and some adapted from older code.

GPL supporters feel that the BSD licence allows others to hoard the work of others without having to give anything back. BSD supporters feel that the GPL takes away fundamental rights from the users, forcing them to write their own software for tasks that are covered by GPL software when the GPL license is used against their will to write proprietary software.

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Legal compatibility

Code licensed under the BSD license can be relicensed under the GPL (is "GPL-compatible") without securing the consent of all original authors. 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 Free Software Foundation provides GNU Lesser General Public License that differs by having a weaker copyleft clause concerning linking of libraries between non-copyleft (proprietary or permissive) licensed code.

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The advertising clause

The original BSD license contained a clause requiring acknowledgments to appear in all advertising materials mentioning the software (see BSD license). The GNU project called this clause "obnoxious", citing the requirement for 75 such acknowledgments when advertising a 1997 version of NetBSD. More importantly, this clause is an additional requirement barred by the GPL, making the original BSD license incompatible with 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.

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External links

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