| In 1991, Linus Torvalds began to work on the Linux kernel while he was attending the University of Helsinki. Torvalds originally created the Linux kernel as a non-commercial replacement for the Minix kernel; he later changed his original non-free license to the GPLv2, which differed primarily in that it also allowed for commercial redistribution. Although dependent on the Minix userspace at first, work from both Linux kernel developers and the GNU project allowed Linux to work with GNU components. Thus Linux filled the last major gap in running a complete, fully functional free operating system. In 2004, Ken Brown of the Alexis de Tocqueville Institution cast doubt on Linus' authorship of Linux, which was rebutted by Minix's author, Andrew S. Tanenbaum. |  |