GNU Project some is released under a weak copyleft or a lax, push-over free software license. The first goal of the GNU project was to create a whole free-software operating system. By 1992, the GNU project had completed all of the major operating system utilities, but had not completed their proposed operating system kernel, GNU Hurd. With the release of the Linux kernel, started independently by Linus Torvalds in 1991, and released under the GPL with version 0.12 in 1992, for the first time it was possible to run an operating system composed completely of free software. Though the Linux kernel is
Operating system Digital Equipment Corporation developed many operating systems for its various computer lines, including TOPS-10 and TOPS-20 time sharing systems for the 36-bit PDP-10 class systems. Before the widespread use of UNIX, TOPS-10 was a particularly popular system in universities, and in the early ARPANET community. RT-11 was a single-user real-time OS for the PDP-11 class minicomputer, and RSX-11 was the corresponding multi-user OS. From the late 1960s through the late 1970s, several hardware capabilities evolved that allowed similar or ported software to run on more than one system. Early systems had utilized microprogramming to implement features on their systems in