Types of Open Source Licenses With as difficult a concept as software freedom to contend with, it is not surprising that many licenses have been proposed to implement it. As of this writing, over fifty approved open source licenses are listed at www.opensource.org . Understanding those licenses would be impossible without a licensing taxonomy, a way of organizing those licenses into appropriate categories. Licenses generally fall into these categories: -
Academic licenses , so named because such licenses were originally created by academic institutions to distribute their software to the public, allow the software to be used for any purpose whatsoever with no obligation on the part of the licen-see to distribute the source code of derivative works. The Berkeley Software Distribution (BSD) license used by the University of California to distribute its software is the archetypal academic license. Academic licenses create a public commons of free software, and anyone can take such software for any purpose ”including for creating proprietary collective and derivative works ”without having to add anything back to that commons. -
Reciprocal licenses also allow software to be used for any purpose whatsoever, but they require the distributors of derivative works to distribute those works under the same license, including the requirement that the source code of those derivative works be published. The GPL license, written by Richard Stallman and Eben Moglen at the Free Software Foundation, is the archetypal reciprocal license. Anyone who creates and distributes a derivative work of a work licensed under a reciprocal license must, in turn , license that derivative work under the same license. Reciprocal licenses, like academic licenses, contribute software into a public commons of free software, but they mandate that derivative works also be placed in that same commons. -
Standards licenses are designed primarily for ensuring that industry standard software and documentation be available to all for implemen-tation of standard products. These licenses sometimes require that any differences from the industry standard be published as a reference implementation so that the standard may evolve if necessary. -
Content licenses ensure that copyrightable subject matter other than software, such as music, art, film, literary works, and the like, be available to all for any purpose whatsoever. These licenses are discussed more fully on the Creative Commons website at www.creativecommons.org . While the Creative Commons goals are not directly related to software freedom , there are many similarities of objective. A few of the software licenses discussed in this book, in particular the Academic Free License (AFL) and the Open Software License (OSL), are appropriate for use with content as well as software, as will be explained in due course. Over the last few years , many organizations and companies have embraced open source software. In the process, they have written many open source licenses that are subtle variants on the academic and reciprocal themes. Those licenses are submitted to Open Source Initiative for review of compatibility with the Open Source Definition and approval as an open source license. There are already over fifty OSI-approved open source licenses. All of the licenses discussed in this book are published at the website run by Open Source Initiative, www.opensource.org . Only approved licenses are listed. Software distributed under any of those licenses is OSI Certified open source software. Open Source Initiative created a certification mark for licensors to display on open source software. As long as an OSI-approved license is used for distribution of the software, such open source software can be marketed with this certification mark:  |
