Linux is covered by what is known as the GNU GPL. The GPL, which is sometimes referred to as a "copyleft" license, was developed for the GNU project by the Free Software Foundation. It makes a number of provisions for the distribution and modification of "free software." "Free," in this sense, refers to freedom, not just cost. The GPL has always been subject to misinterpretation, and we hope that this summary will help you to understand the extent and goals of the GPL and its effect on Linux. A complete copy of the GPL is available at http://www.gnu.org/copyleft/gpl.html.
Originally, Linus Torvalds released Linux under a license more restrictive than the GPL, which allowed the software to be freely distributed and modified, but prevented any money changing hands for its distribution and use. The GPL allows people to sell and make profit from free software, but doesn't allow them to restrict the right for others to distribute the software in any way.
1.4.1. A Summary of Free Software Licensing
First, we should explain that "free software" covered by the GPL is not in the public domain. Public domain software is software that is not copyrighted and is literally owned by the public. Software covered by the GPL, on the other hand, is copyrighted to the author or authors. This means that the software is protected by standard international copyright laws and that the author of the software is legally defined. Just because the software may be freely distributed doesn't mean it is in the public domain.
GPL-licensed software is also not "shareware ." Generally, shareware software is owned and copyrighted by the author, but the author requires users to send in money for its use after distribution. On the other hand, software covered by the GPL may be distributed and used free of charge.
The GPL also allows people to take and modify free software, and distribute their own versions of the software. However, any derived works from GPL software must also be covered by the GPL. In other words, a company could not take Linux, modify it, and sell it under a restrictive license. If any software is derived from Linux, that software must be covered by the GPL as well.
People and organizations can distribute GPL software for a fee and can even make a profit from its sale and distribution. However, in selling GPL software, the distributor can't take those rights away from the purchaser; that is, if you purchase GPL software from some source, you may distribute the software for free or sell it yourself as well.
This might sound like a contradiction at first. Why sell software for profit when the GPL allows anyone to obtain it for free? When a company bundles a large amount of free software on a CD-ROM and distributes it, it needs to charge for the overhead of producing and distributing the CD-ROM, and it may even decide to make profits from the sale of the software. This is allowed by the GPL.
Organizations that sell free software must follow certain restrictions set forth in the GPL. First, they can't restrict the rights of users who purchase the software. This means that if you buy a CD-ROM of GPL software, you can copy and distribute that CD-ROM free of charge, or you can resell it yourself. Second, distributors must make it obvious to users that the software is indeed covered by the GPL. Third, distributors must provide, free of charge, the complete source code for the software being distributed, or they must point their customers on demand to where the software can be downloaded. This will allow anyone who purchases GPL software to make modifications to that software.
Allowing a company to distribute and sell free software is a very good thing. Not everyone has access to the Internet to download software, such as Linux, for free. The GPL allows companies to sell and distribute software to those people who do not have free (cost-wise) access to the software. For example, many organizations sell Linux on floppy, tape, or CD-ROM via mail order, and make a profit from these sales. The developers of Linux may never see any of this profit; that is the understanding that is reached between the developer and the distributor when software is licensed by the GPL. In other words, Linus knew that companies might wish to sell Linux and that he might not see a penny of the profits from those sales. (If Linus isn't rich, at least he's famous!)
In the free-software world, the important issue is not money. The goal of free software is always to develop and distribute fantastic software and to allow anyone to obtain and use it. In the next section, we'll discuss how this applies to the development of Linux.
1.4.2. SCO and Other Challenges
In March 2003, a company called SCOwhich had a tortuous history of mergers and divestitures that involved purchasing some rights to Unixclaimed that Linux contained some source code to which SCO had rights, and therefore that SCO had rights to Linux as well. The company started by suing IBM, a bold choice (to say the least) because few companies in the computer field could be more familiar with litigation or be better prepared for it. In any case, SCO made it clear that their complaints went far beyond IBM; indeed, that they were owed something by anyone using Linux. In December 2003, according to news reports, SCO even sent letters to a large number of Fortune 1000 companies advising them to send licensing fees to SCO.
Red Hat and other companies joined the fray. Novell, which by then had bought SUSE and become a solid member of the Linux community, added some zest to the already indigestible controversy by citing its own rights to Unix. Over time the whole affair became a tangle of lawsuits, countersuits, motions to dismiss, public relations grand-standing, and general mud-slinging.
As of this writing, the SCO case is unresolved, but the results seem salutory. Few observers believe Linux is in trouble; rather, it is SCO that is financially threatened. The network of companies, individuals, and key organizations that support Linux has handled the challenge well. Some major vendors strengthened their support for Linux by offering their customers indemnification. The next edition of this book, we hope, will contain little more than a footnote about the whole affair.
Finally, Linus Torvalds and the OSDL have recognized that the old method of accepting code with no strings attached should be tightened. Starting in May 2004, anyone submitting code to the kernel has been asked to include their contact information and to declare informally that they have a right to the code they are submitting. The new system is lightweight and simple, but allows challenges (of which none have been received yet) to be tracked back to the people responsible for the code in question.
Further copyright challenges to Linux are unlikely; patents, however, could be used against it. But every programmer and software company has to worry about software patents; Linux and free software are no more at risk than any other software. Although the workings of free software are entirely open to inspection, and therefore might be more tempting to target with a patent lawsuit, the only purpose of such a lawsuit would be to maliciously shut down a project, because free software cannot support license fees.