Linux (commonly pronounced IPA: /ˈlɪnəks/ in English; variants exist[1]) is a generic term referring to Unix-like computer operating systems based on the Linux kernel. Their development is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed by anyone under the terms of the GNU GPL[2] and other free licenses. Linux distributions are predominantly known for their use in servers, although they are installed on a wide variety of computer hardware, ranging from embedded devices and mobile phones to supercomputers,[3] and their popularity as a desktop/laptop operating system has been growing lately due to the rise of netbooks and the Ubuntu distribution of the operating system.[4][5] The name "Linux" comes from the Linux kernel, originally written in 1991 by Linus Torvalds. The rest of the system, including utilities and libraries, usually comes from the GNU operating system announced in 1983 by Richard Stallman. The GNU contribution is the basis for the alternative name GNU/Linux.[6]