Here's the opening paragraphs from wikipedia:http://en.wikipedia.org/wiki/FOSS
"From the early 90s onward, alternative terms for free software have come into common use, with much debate in the free software community. The term "free software" was coined by Richard Stallman in 1983 when he launched the free software movement. Records of published version of its definition can be found dating back to February 1986. The definition can be summarised as software which the user can use for any purpose, study the source code of, adapt to their needs, and redistribute - modified or unmodified. To avoid the ambiguity of the English word "free" (free as in beer versus free as in speech), and to avoid talking about the impact on freedom of non-free software, people have suggested alternative names.
"Open-source software", "Software Libre", "FLOSS" (Free/Libre/Open-Source Software), and "FOSS" (Free and Open-Source Software) are the most common alternative terms. The most popular of these has been "open-source software".
Users of each of these terms share almost identical licence criteria and development practices, but differ, according to Richard Stallman, in the respective philosophical values. Some people use "libre" (as in free speech) or "gratis" (as in free beer) to avoid the ambiguity of the word "free". However, these terms are mostly used within the free software movement and are slowly spreading. "