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# 1.5 About Linux's Copyright

Linux is covered by what is known as the GNU General Public License, or GPL. The GPL was developed for the GNU project by the Free Software Foundataion. 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 included in Appendix E.

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. On the other hand, the GPL allows people to sell and make profit from free software, but does not allow them to restrict the right for others to distribute the software in any way.

First, it should be explained that ``free software'' covered by the GPL is not in the public domain. Public domain software is software which 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 does not mean that 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.

The GPL allows free software to be distributed and used free of charge. However, it also allows a person or organization to distribute GPL software for a fee, and even to make a profit from its sale and distribution. However, in selling GPL software, the distributor cannot 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? As an example, let's say that some company decided to bundle a large amount of free software on a CD-ROM and distribute it. That company would need to charge for the overhead of producing and distributing the CD-ROM, and the company may even decide to make profit from the sales of software. This is allowed by the GPL.

Organizations which sell free software must follow certain restrictions set forth in the GPL. First, they cannot 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 resell it yourself. Secondly, distributors must make it obvious to users that the software is indeed covered by the GPL. Thirdly, distributors must provide, free of charge, the complete source code for the software being distributed. This will allow anyone who purchases GPL software to make modifications of 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 diskette, tape, or CD-ROM via mail order, and make 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 may wish to sell Linux, and that he may not see a penny of the profits from those sales.

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.

Next: 1.6 The Design and Up: 1 Introduction to Linux Previous: 1.4.8 Other applications