April 3, 1991 — AT&T Sues BSD

The development of technology is influenced not only by great achievements, discoveries, and economic events, but also by legal and court events. The dispute between AT&T and the University of Berkeley significantly changed the balance of power between operating systems and influenced the entire history of the IT industry.

What happened?

In the 1970s Bell Labs, which was part of AT&T, developed the UNIX operating system and distributed it to many companies and universities. In the 1980s the BSD project (Berkeley Software Distribution) appeared at the University of Berkeley. At first it was a package of additions to UNIX; later it became a separate operating system.

In April 1991 AT&T, through its subsidiary Unix System Laboratories, filed a lawsuit against BSDi, claiming that BSD/386 used code from UNIX System V.

1992 — preliminary court injunctions

The court temporarily prohibited the distribution of BSD/386 and some source code, which practically stopped the development of free BSD systems.

1993 — negotiations and partial settlement

After long disputes the parties began negotiations, discussing the removal of disputed fragments of code from BSD.

1994 — final agreement

AT&T (already through Novell, which had acquired USL) and the University of California at Berkeley reached an agreement: several files were removed from BSD, and the rest of the system became free for distribution.

1994 — release of 4.4BSD-Lite

After the settlement Berkeley released 4.4BSD-Lite — a version of the system without AT&T code, which became the basis for FreeBSD, NetBSD, and OpenBSD.

Consequences

During three years of litigation, many companies were afraid to use BSD — if AT&T had won, they could have become violators of AT&T copyrights. During this time, companies were looking for an alternative freely distributed operating system, and many chose Linux.

Linux, which appeared in 1991, was significantly inferior to BSD, but it was legally clean. During the most important period of operating system growth, companies and users who could have chosen BSD chose Linux instead. By the time the case between AT&T and BSD ended, many companies had already built their environments on Linux.

Linus Torvalds (the creator of Linux) has repeatedly stated that this lawsuit changed the history of Linux.

Thus, because of legal disputes that essentially ended with almost nothing, the history of operating systems pushed aside one of its most important players and brought forward a new one that still dominates in many areas today.