GNU/Linux is free software. This simple assertion hides a complex reality, but perhaps best captures the fundamental rift in philosophy between open- and closed-source software. To quote the Free Software Foundation's web page, ```free' is meant in the sense of `free speech', not `free beer'.'' There are several licensing arrangements for GNU/Linux and related software. The best-known is the GNU General Public License (GPL), which stipulates roughly that the ``source code'' must not only be freely available, but it must remain freely available in all derivative works. There is nothing to prohibit (or discourage) selling ``free software'' for a profit, but it violates the GPL to restrict the liberty of the buyer to distribute the same product as they see fit. It is encouraged that users copy and distribute free software, make changes and improvements, or package it for others' use. The GPL is the antithesis of the traditional End-User License Agreement (EULA), in which the ``buyer'' does not actually own the software or the medium on which the software is sold, and has no right to distribute the software to others, to change the software in any way, or even to run more than one copy of the software on several machines (without paying for a multi-user license). Not all GNU/Linux software is GPL-ed. There are other types of license agreement, and some software bundled with commercial Linux distributions (see below) is outright commercial, and/or governed by a restrictive EULA.
The original goal of the free software movement was to provide a stable, free replacement for the mainframe operating system Unix. That goal has grown to include open-source programs to perform all manner of computer tasks. To name just a few: word processing and professional-quality typesetting; web browsing, email, instant messaging, and chat; sound creation and manipulation, CD burning; image manipulation, real-time animation, ray tracing, and computer-aided design; secure (encrypted) file transfer and remote login. When it comes to networking and security, open-source software is as good or better than commercial products.
Liberty aside, GNU/Linux is also relatively inexpensive. A commercial distribution (which may include non-GPL software) costs about $50-80 (U.S.), and a GPL GNU/Linux CD system may be purchased for $1-10, depending on the distribution and the source. GNU/Linux GPL distributions may be downloaded at no cost from the web. This state of affairs leaves many potential users (especially in the business world) wondering, ``What's the catch?'' Perhaps it is better to ask, ``Why should a software company be able to gouge computer users--and limit what they can do with their computer--by providing an expensive yet inadequately supported and almost wholly inferior product, and why do consumers not only tolerate this, but ardently defend the monopolistic supplier?'' The answer is in part that users are unaware of how their computer works (and are unwilling or afraid to learn), and therefore are prepared to put their trust in an expensive product that promises trouble-free use, whether or not the product actually delivers on this claim.