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Author: Bruce Byfield

The GNU General Public License (GPL) is one of the most widely used software licenses — and, undoubtedly, the most misunderstood. Some of this misunderstanding comes from hostile propaganda, but some also comes from a lack of experience in licensing issues on the part of both lawyers and lay users, and the use of standard language in conventional end-user license agreements that are unthinkingly coupled with the GPL. In all cases, the confusion is frequently based on misreadings, rumors, secondhand accounts, and what is convenient to believe.

To get a sense of the most common misunderstandings, NewsForge consulted with three experts: Richard Fontana, a lawyer with the Software Freedom Law Center and one of the main drafters of the third version of the license; David Turner, former compliance engineer at the Free Software Foundation who is assisting with the revisions of the license; and Harald Welte of the GPL-Violations project, which tracks possible cases of non-compliance and tries to assist in resolving them. Taken together, the opinions of these experts offers a summary of the most common misunderstandings about the GPL, from comic exaggerations to potentially legitimate differences of opinion.


1. The GPL is viral

The idea that any software that comes into contact with GPL-licensed software also becomes subject to the GPL seems to have originated with Craig Mundie, a senior vice president of Microsoft, in a speech delivered at the New York University Stern School of Business in May 2001. Since then, David Turner reports, many people have come to believe that even having GPL software on the same computer brings other software under the license. In extreme cases, Turner says, this belief has lead to bans on all GPL software at some companies.

This misunderstanding stems from section 2 of the current GPL, which states only that modified versions of GPL software must also be licensed under the GPL. However, the section clearly states that if a program “can be reasonably considered independent and separate works in themselves, then the GPL does not apply to it” and that being on the same “storage or distribution medium does not bring the other work under the scope of this License.” As Fontana points out, the definition of a derivative work could be clearer — and should be in the third version of the license — but the general principle is unmistakable.


2. The GPL is unenforceable

At the opposite extreme from the idea that the GPL is viral is that it is unenforceable — or, in Turner’s words, “It’s just a bunch of hippies. How are they going to force us to do anything?” Turner attributes this misconception at least partly to the Free Software Foundation’s preference for helping violators come into compliance rather than resorting automatically to lawyers and the courts. Yet this preference can also be reversed; the fact that violators consistently prefer compliance to a legal battle strongly suggests that they believe the license would be enforced. More importantly, in the few cases where the GPL has gone to court, such as Welte v. Sitecom in Germany or Drew Technologies, Inc. v. Society of Automotive Engineers, Inc. in the United States, the license has been indirectly or directly upheld.


3. You can’t charge for GPL software

Some of the first words in the GPL are, “When we speak of free software, we are referring to freedom, not price.” Yet despite repeated reminders from the Free Software Foundation, including one on its home page, even some members of the free software communities believe that charging money for GPL software is illegal. Dozens of companies, including Red Hat and Novell, who continue to charge for free software, daily prove otherwise.

The only mentions of price in the GPL come in section 1, which states that, “You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee,” and section 3b, which states that source code must be provided “for a charge no more than your cost of physically performing source distribution.”


4. The “liberty or death” clause applies absolutely

Section 7 of the GPL is sometimes tagged as the “liberty of death” clause because it states that conditions imposed by court orders or allegations of patent infringement do not release users of the license from following its conditions. Instead, if they cannot meet both the imposed conditions and the GPL’s conditions, they must stop distributing.

According to Fontana, many users interpret section 7 far too rigorously. Although the section applies only to patent licenses that prohibit users from passing on full GPL rights, Fontana says, “Some read the section as prohibiting distribution of GPLed code under the benefit of any non-sublicensable patent license.” In addition, “some have worried about the existence of a possibly-applicable patent, or of some law or regulation that might potentially be applied to everyone in a particular jurisdiction is enough to trigger this jurisdiction.” Neither reading is supported by the actual text of the license.


5. Distributors only need to ship the source code they alter

Section 5 of the GPL states that “by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions.” These conditions include the obligation to provide the source code of the works distributed. However, many maintainers of software derived from other works conveniently believe that, so long as the distributors of the original work are distributing source code, they only need to provide the source code for the works that they modify. As mentioned in a recent NewsForge article, this assumption seems especially widespread among maintainers of derivative GNU/Linux distributions. Unfortunately, while the need for all distributors to provide source code sometimes seems redundant and often onerous, the GPL does not allow any provisions for exceptions. Nor is it likely to in the future, according to Turner.


6. Distributors only need to supply source code, and not the means to use it

Under section 3 of the GPL, providing the source code is only part of a distributor’s obligation. The section defines the complete source code as not only “the source code for all modules” and “any associated interface definition files,” but also “the scripts used to control compilation and installation of the executable” — in other words, the tools needed to make the source code useful to anyone. Within the free software community, many people will already have those tools, but distributors cannot assume that all recipients will.


7. Distributors don’t need to provide offers of source code

The GPL in section 3 permits users to either distribute source code with binary files, or to include an offer to provide the source code. To do neither and wait for requests may be less work, but is a straightforward violation.


8. Distributors only need to offer source code to their customers

If distributors opt to provide an offer for source code, then under section 3b, the offer must be good for three years, and must apply to “any third party.” No distinction is made between commercial customers and anyone else who might be interested in the source code.


9. Distributors only need to link to the license text

Providing only a link to the GPL is easy for the distributor, but a clear violation of section 1, which grants the right to distribute GPL software “provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice.” Welte explains that this provision is necessary because all users may not always have Internet access to read the license. If they cannot read the license, they cannot understand the terms under which they are allowed to distribute the software.


10. I don’t think that word means what you think it means

Richard Fontana points out that a handful of confusions about the GPL are not misunderstandings, but potentially valid differences based on differences of opinion or interpretation under law. “Perhaps the most fundamental difference,” he says, “has to do with what a ‘work’ of software is, in the copyright law sense. The GPL assumes that the underlying legal system will provide a reasonable answer to this question. The work includes what a programmer would objectively regard as being part of the same program.” However, others with different philosophies or approaches to the issue might define different works in other terms, such as the files that they use.

Similarly, while the current version of the GPL refers to “distribution” of a work, Fontana notes that the word can have different legal meanings. For example, he says, “The meaning may vary in the United States depending on whether one is talking about distribution in the copyright law sense or distribution in the sense of ordinary commercial usage.” Moreover, in other countries, “distribution” or its equivalent may not occur in copyright law, or be used in a different sense.

One of the main goals of the latest draft of the new version of the GPL is to reduce these ambiguities by starting the license with definitions and changing terminology. “Distribution,” for instance, has been replaced with “propagate” and “convey.” But, until the third version is finalized in early /2007/, the problems of definition will remain.


Future misunderstandings

Many misunderstandings about the GPL may be eliminated or reduced by the next version of the license, which, so far, has included many attempts to clarify its intentions. In fact, Turner believes that the extensive consultation that is part of the revision process may educate users in itself. “Here,” he says, “is their chance to discuss the license publicly. They can read the discussion and see how the Free Software Foundation came to its decisions. It gives people an information pool.”

At the same time, the upcoming changes may create their own set of misunderstandings. After all, one of the reasons for the revision is to take into account new considerations, such as BitTorrent distributions, that did not exist when the current text was written. In addition, while changes in terminology may make the license easier to apply in different jurisdictions, those familiar with the old terms may be confused. Turner wonders whether the old terms will “stick around, if only subliminally, and will confuse people.”

In the end, Turner concedes, some degree of confusion is probably inescapable. “There’s always going to be people who misunderstand,” he says, “no matter how you write the license, even in words of one syllable.”


Bruce Byfield is a course designer and instructor, and a computer journalist who writes regularly for NewsForge, Linux.com and IT Manager’s Journal.