Berkeley Software Distribution (also known as BSD or Berkeley Unix) was the first freely licensed Unix-like operating system developed by the Computer Science Research Group (CSRG) of the University of California, Berkeley, from 1977 to 1995. BSD went on to spawn multiple derivatives including FreeBSD, OpenBSD, NetBSD, and most notably, Darwin — which became the foundation for Apple’s Macintosh OS and iOS operating systems now in use by hundreds of millions of people.