Linux
Linux is a free operating-system kernel first announced by Linus Torvalds on 25 August 1991, in a Usenet post describing "just a hobby, won't be big and professional like gnu" for 386 AT clones. It is the kernel — the program that allocates the machine's resources to other programs — normally used with the GNU Project's software to form the complete system Richard Stallman calls GNU/Linux; GNU had been under construction since January 1984 and was complete except for a kernel when Linux appeared. The kernel is released under GNU GPL version 2; the FSF's licence history runs from version 1 in 1989 and version 2 in June 1991 to version 3 released on 29 June 2007 — a revision whose anti-tivoization terms the Linux developers declined to adopt. Kernel development now follows a steady cadence: one mainline release every 9–10 weeks maintained by Torvalds, backported stable releases, and longterm kernels such as 6.12 kept alive until December 2028. Distributions turn the kernel into products and services — Red Hat Enterprise Linux, Debian, Fedora, openSUSE, Ubuntu and SUSE Linux Enterprise among them — sold by Red Hat under subscriptions, with Red Hat acquired by IBM on 9 July 2019. Dated figures in this article carry the year of the source that recorded them.