Linux ( / ˈ l iː n ʊ k s/ ( listen) LEE-nuuks or / ˈ l ɪ n ʊ k s/ LIN-uuks) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds.
GPLv2 and others (the name 'Linux' is a trademark )