Into the gap left by the Free Software Foundation's uncompleted HURD had stepped a Helsinki University student named Linus Torvalds. In 1991 he began developing a free Unix kernel for 386 machines using the Free Software Foundation's toolkit. His initial, rapid success attracted many Internet hackers to help him develop Linux, a full-featured Unix with entirely free and re-distributable sources.
Linux was not without competitors. In 1991, contemporaneously with Linus Torvalds's early experiments, William and Lynne Jolitz were experimentally porting the BSD Unix sources to the 386. Most observers comparing BSD technology with Linus's crude early efforts expected that BSD ports would become the most important free Unixes on the PC.
The most important feature of Linux, however, was not technical but sociological. Until the Linux development, everyone believed that any software as complex as an operating system had to be developed in a carefully coordinated way by a relatively small, tightly-knit group of people. This model was and still is typical of both commercial software and the great freeware cathedrals built by the Free Software Foundation in the 1980s; also of the freeBSD/netBSD/OpenBSD projects that spun off from the Jolitzes' original 386BSD port.
Linux evolved in a completely different way. From nearly the beginning, it was rather casually hacked on by huge numbers of volunteers coordinating only through the Internet. Quality was maintained not by rigid standards or autocracy but by the naively simple strategy of releasing every week and getting feedback from hundreds of users within days, creating a sort of rapid Darwinian selection on the mutations introduced by developers. To the amazement of almost everyone, this worked quite well.
By late 1993 Linux could compete on stability and reliability with many commercial Unixes, and hosted vastly more software. It was even beginning to attract ports of commercial applications software. One indirect effect of this development was to kill off most of the smaller proprietary Unix vendors -- without developers and hackers to sell to, they folded. One of the few survivors, BSDI (Berkeley Systems Design, Incorporated), flourished by offering full sources with its BSD-based Unix and cultivating close ties with the hacker community.
These developments were not much remarked on at the time even within the hacker culture, and not at all outside it. The hacker culture, defying repeated predictions of its demise, was just beginning to remake the commercial-software world in its own image. It would be five more years, however, before this trend became obvious.