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Reciprocity and the GPL

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The world of software was transformed by the GNU General Public License. This chapter details the history and the ins and outs of this particular scheme of copyright licensing, and how it can be manifested legally when purchasing software.
This chapter is from the book

The GPL Bargain

The world of software was transformed by the GNU General Public License. The word GNU in the license name is a play on words by the license author, Richard Stallman. "The name GNU was chosen following a hacker tradition," he says, "as a recursive acronym for 'GNU's Not Unix.'" Throughout the world, the license is mostly referred to simply as the GPL. (The GPL is reprinted in the Appendices.)

The GPL has been enormously influential in creating a large public commons of software that is freely available to everyone worldwide. As the GPL advocates might describe it in political tones, they have prevented much software from being captured by proprietary software interests and converted into restricted private property for personal gain. The GPL is both praised and reviled for that accomplishment.

The bargain created by the GPL can be paraphrased simply as follows: You may have this free software on condition that any derivative works that you create from it and distribute must be licensed to all under the same license.

Here's how the GPL actually says it:

You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License. (GPL, Section 2.)

This is the most powerful idea in the GPL and the one that has aroused the most passion in its adherents and its detractors.

Adherents of the GPL suggest that this provision protects free software. It guarantees that all derivative works of GPL-licensed software will also be GPL-licensed software. Licensees cannot selfishly remove their improvements from the public commons. Derivative work software will always be free and open. The result is a dynamic and ever growing collection of GPL-licensed software that can be reused and improved.

Detractors say that this provision creates an island of software from which only GPL-licensed software can escape. The rest of the world cannot share the benefits of the source code of GPL-licensed software unless they are willing to travel to that island and commit to using the GPL license for their works.

Some of these GPL detractors are licensors of proprietary software. Their complaints are hypocritical. They too have created islands of software from which nothing can escape.

The only principled complaint about the GPL comes from those who license their software under academic open source licenses. Such software can be incorporated into GPL-licensed software but the converse is not true. In one sense, academic licenses are for generous donors of software, and the GPL and other reciprocal licenses are for generous sharers of software. Because of the GPL we have two—not just one—public commons of free software.

This book is not the place to resolve this ongoing debate. It is enough to say that licensors are free to decide what licensing model suits them best and whether or how to give away rights. Licensees may accept or reject software under the terms of the license, but they don't get to set their own terms. That's what copyright law allows, and the GPL uses that law effectively and brilliantly for its avowed purpose of fostering the creation of free software available to all under a single license.

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