Alternative terms for free software have been a controversial issue among free software users from the late 1990s onwards. Coined in 1983 by Richard Stallman, "free software" is used to describe software which can be used, modified, and redistributed with little or no restriction. These freedoms are formally described in The Free Software Definition, first published in February 1986.
Alternatives for "free software" were sought for marketing purposes and because of a perceived "moralising and confrontational" attitude that had been associated with the term. In addition, the "available at no cost" ambiguity of the word "free" was seen as discouraging business adoption. In a 1998 strategy session in California, "open source software" was selected by Todd Anderson, Larry Augustin, Jon Hall, Sam Ockman, Christine Peterson, and Eric S. Raymond. Richard Stallman had not been invited. The session was arranged in reaction to Netscape's January 1998 announcement of a source code release for Navigator (as Mozilla). Those at the meeting described "open source" as a "replacement label" for free software  and Open Source Initiative was soon-after founded by Eric Raymond and Bruce Perens to promote the term as part of "a marketing program for free software". Stallman and others object to the term "open source software" because it does not make people think of the freedoms that the software in question gives users.
Each of the terms "free software" and "open source software" has fans and critics. Partly because of the failure to adopt one specific term, other terms have been proposed. These include "Software Libre" (or libre software), "FLOSS" (Free/Libre/Open Source Software), and "FOSS" (or F/OSS, Free and Open Source Software). These terms share almost identical licence criteria and development practices.
The first known use of the phrase "free open source software" on Usenet was in a posting on 18 March, 1998, just a month after the term "open source" itself was coined. In February 2002, "F/OSS" appeared on a Usenet newsgroup dedicated to Amiga computer games. In early 2002, MITRE used the term "FOSS" in what would later be their 2003 report Use of Free and Open Source Software (FOSS) in the U.S. Department of Defense.
"FLOSS" was used in 2001 as a project acronym by Rishab Aiyer Ghosh as an acronym for free/libre/open source software. Later that year, the European Commission (EC) used the phrase when they funded a study on the topic.
Unlike "libre software", which aimed to solve the ambiguity problem, "FLOSS" aimed to avoid taking sides in the debate over whether it was better to say "free software" or to say "open source software".
Proponents of the term point out that parts of the FLOSS acronym can be translated into other languages, with for example the "F" representing free (English) or frei (German), and the "L" representing libre (Spanish or French), livre (Portuguese), or libero (Italian), and so on. However, this term is not often used in official, non-English, documents, since the words in these languages for "free as in freedom" do not have the ambiguity problem of English's "free".
Richard Stallman endorses the term FLOSS to refer to "open source" and "free software" without necessarily choosing between the two camps, however, he asks people to consider supporting the "free software" camp. Stallman has suggested that the term "unfettered software" would be an appropriate, non-ambiguous replacement, but that he would not push for it because there was too much momentum and too much effort behind the term "free software".
"Software Libre" was first used publicly in 2000, by the European Commission. The word "libre", borrowed from the Spanish and French languages, means having liberty. This avoids the freedom/cost ambiguity of the word "free".
The free software community in India sometimes uses the term "Swatantra software" since the term "Swatantra" means free in Sanskrit, which is the ancestor of all Indo-European Languages of India, including Hindi, despite English being the lingua franca.
In The Philippines, "malayang software" is sometimes used. The word "libre" exists in the Filipino language, and it came from the Spanish language, but has acquired the same cost/freedom ambiguity of the English word "free".
None of these terms, or the term "free software" itself, have been trademarked. Bruce Perens of OSI attempted to register "open source" as a service mark for OSI in the United States of America, but that attempt failed to meet the relevant trademark standards of specificity. OSI claims a trademark on "OSI Certified", and applied for trademark registration, but did not complete the paperwork. The United States Patent and Trademark Office labels it as "abandoned".
While the term "free software" is associated with FSF's definition, and the term "open source software" is associated with OSI's definition, the other terms have not been claimed by any group in particular. FSF's and OSI's definitions are worded quite differently but the set of software that they cover is almost identical.
All of the terms are used interchangeably, the choice of which to use is mostly political (wanting to support a certain group) or practical (thinking that one term is the clearest).
The choice of term has little or no impact on which licences are valid. The vast majority of software referred to by these terms is distributed under a small set of licences, all of which are unambiguously accepted by the various de facto and de jure guardians of each of these terms. 50-70% of this software is under the GNU General Public License, and most of the rest is distributed under the terms of the GNU Lesser General Public License, the BSD licenses, the Mozilla Public License, the MIT License, and the Apache License, each with a share of between 2% and 10%.
Apart from these two organisations, the Debian project is seen by some to provide useful advice on whether particular licences comply with their Debian Free Software Guidelines. Debian does not publish a list of "approved" licences, but its judgments can be tracked by checking what licences are used by software they have allowed into their distribution. In addition, the Fedora project does provide a list of approved licenses (for Fedora) based on approval of the Free Software Foundation (FSF), the Open Source Initiative (OSI), and consultation with Red Hat Legal. 
There is also a class of software that is covered by the names discussed in this article, but which doesn't have a licence: software for which the source code is in the public domain. The use of such source code, and therefore the executable version, is not restricted by copyright and therefore does not need a free software licence to make it free software.