Linux is widely known as the "free" operating system, yet some companies actually sell their distributions of Linux. What's that all about?
Well, it all depends on which definition you are using when you are describing the software. The distinction is between the concepts of freedom and free-of-charge. In the Linux world, the two concepts are often called "free as in speech" and "free as in beer" respectively.
Wikipedia (http://en.wikipedia.org/wiki/Gratis_versus_Libre) draws the distinction between "free as in speech" (libre) and "free as in beer" (gratis) like this:
In hacker slang, gratis is typically referred to as free as in beer while libre is referred to as free as in speech. Free as in beer refers to things which are available at no monetary cost (like free beer at a party). By contrast, the expressions free as in speech, free as in freedom, and free as in rights, refer to something which is free of any and all restrictions, as in the freedom of speech.Wikipedia
Since the advent of the free software movement, these terms have entered frequent use for categorising computer programs according to the licenses and legal restrictions that cover them, such as copyright and patents. Both this expression and the term gratis are used to distinguish freeware (gratis software) from free software.
OK, so something can be "free as in speech" without being "free as in beer". (Is it any wonder that the English language is so difficult to learn?) There are several other related terms that probably need to be defined and compared as well. The table below compares some of the characteristics of software that is "free" (no charge, gratis), "free and open source" (libre), "closed source," "proprietary," and "non-free." To be clear, the table is meant to illustrate the rights of the average user, not the rights of a reseller, redistributor or other vendor. Note also that there is some ambiguity over the actual definition of certain terms such as "non-free." This table makes no attempt to resolve that ambiguity. It also does not address "freeware" or "shareware."
For more detailed descriptions of each term, use the hyperlinks above. They take you to some of the Wikipedia entries for each. (You may want a bottle of headache remedy within easy reach before you do that!)
The Codebreakers is a two-part documentary, originally aired on BBC World TV during May 2006. It discusses the use of Free and Open Source Software (FOSS) to help develop poor countries. It also includes some very interesting stories and interviews. I am making this available, here, under the terms of its Creative Commons Attribution 2.5 license. See http://www.apdip.net/news/fossdoc for more infomation.
Theme music for the Going Linux podcast is generously provided by Mark Blasco. http://www.podcastthemes.com
Going Linux Podcast by Larry Bushey is licensed under a Creative Commons Attribution 4.0 International License.