OSS

Free and open-source software (F/OSS, FOSS) or free/libre/open-source software (FLOSS) is software that is both free software and open source It is liberally licensed to grant users the right to use, copy, study, change, and improve its design through the availability of its source code This approach has gained both momentum and acceptance as the potential benefits  have been increasingly recognized by both individuals and corporations

In the context of free and open-source software, free refers to the freedom to copy and re-use the software, rather than to the price of the software The Free Software Foundation, an organization that advocates the free software model, suggests that, to understand the concept, one should "think of free as in free speech, not as in free beer"

FOSS is an inclusive term that covers both free software and open source software, which despite describing similar development models, have differing cultures and philosophies Free software focuses on the fundamental freedoms it gives to users, whereas open source software focuses on the perceived strengths of its peer-to-peer development model FOSS is a term that can be used without particular bias towards either political approach

Free software licences and open source licenses are used by many software packages While the licenses themselves are in most cases the same, the two terms grew out of different philosophies and are often used to signify different distribution methodologies

Linux and OSS

Linux and most GNU software are licensed under the GNU General Public License (GPL). The GPL requires that anyone who distributes Linux must make the source code (and any modifications) available to the recipient under the same terms. Other key components of a software system may use other licenses; many libraries use the GNU Lesser General Public License (LGPL), a more permissive variant of the GPL, and the X.org implementation of the X Window System uses the MIT License.

Torvalds states that the Linux kernel will not move from version 2 of the GPL to version 3. He specifically dislikes some provisions in the new license which prohibit the use of the software in digital rights management, and it would also be impractical to obtain permission from all the copyright holders, who number in the thousands.

A 2001 study of Red Hat Linux 7.1 found that this distribution contained 30 million source lines of code. Using the Constructive Cost Model, the study estimated that this distribution required about eight thousand man-years of development time. According to the study, if all this software had been developed by conventional proprietary means, it would have cost about $1.46 billion (2012 US dollars) to develop in the United States.

Most of the code (71%) was written in the C programming language, but many other languages were used, including C++, Lisp, assembly language, Perl, Python, Fortran, and various shell scripting languages. Slightly over half of all lines of code were licensed under the GPL. The Linux kernel itself was 2.4 million lines of code, or 8% of the total.

In a later study, the same analysis was performed for Debian GNU/Linux version 4.0 (etch, which was released in 2007). This distribution contained close to 283 million source lines of code, and the study estimated that it would have required about seventy three thousand man-years and cost US$8.04 billion (in 2012 dollars) to develop by conventional means.

In the United States, the name Linux is a trademark registered to Linus Torvalds. Initially, nobody registered it, but on 15 August 1994, William R. Della Croce, Jr. filed for the trademark Linux, and then demanded royalties from Linux distributors. In 1996, Torvalds and some affected organizations sued him to have the trademark assigned to Torvalds, and in 1997 the case was settled. The licensing of the trademark has since been handled by the Linux Mark Institute. Torvalds has stated that he trademarked the name only to prevent someone else from using it. LMI originally charged a nominal sublicensing fee for use of the Linux name as part of trademarks, but later changed this in favor of offering a free, perpetual worldwide sublicense.

GNU/Linux
The Free Software Foundation views Linux distributions that use GNU software as GNU variants and they ask that such operating systems be referred to as GNU/Linux or a Linux-based GNU system. The media and common usage, however, refers to this family of operating systems simply as Linux, as do many large Linux distributions (e.g. SUSE Linux and Mandriva Linux). Some distributions, notably Debian, use GNU/Linux. The naming issue remains controversial.