Programming languages and software engineering - The Computing Universe: A Journey through a Revolution - page 73

that allowed free use of the source code. Importantly, the license allowed the
possibility of incorporating all or part of the Berkeley software in a closed-source
commercial product. The license only required that any copyright notices in the
code were maintained along with the disclaimer of any warranty.
The 1980s were a confusing time for the Unix community. By this time,
AT&T had realized that Unix was a very valuable software product and, under
the terms of a new antitrust settlement in 1984, the company began charging for
the Unix software. By 1992, friction between AT&T's new, commercially focused
Unix Systems Laboratories division and the freewheeling Berkeley open-source
community had come to a head. AT&T began a court case against the University
of California. In addition to these legal problems, many different and incom-
patible variants of Unix had been spun-off - “forked” - from the original open-
source Unix code, leading to a very fragmented Unix development community.
Meanwhile, at MIT, a software developer in the AI lab named Richard Stallman
( B.4.8 ) had become concerned about the loss of community that happened when
software could not be freely shared. In 1984, Stallman founded the Free Software
Foundation ( B.4.9 ) with the goal of developing “an entirely free operating sys-
tem that anyone could download, use, modify, and distribute freely.” 20 He named
his project GNU, standing for “GNU's Not Unix.” To ensure that the source code
remained open and freely shareable, Stallman devised the GNU Public License
(GPL) that is very different from the permissive Berkeley BSD open-source license.
The GPL license requires that any modifications of the software must be released
under the same GPL open-source license. More important for commercial soft-
ware companies was the “viral” requirement that any software formed by com-
bining free, GPL-licensed software with commercial software must all be released
under a free GPL license. Under the GNU umbrella, Stallman created some very
popular tools for writing software that are still widely used by the computer
science community - the GNU Emacs text editor, the GCC compiler, and the GDB
debugger. However, it was left to a young Finnish graduate student named Linus
Torvalds ( B.4.10 ) to reunite the Unix community around his version of the Unix
kernel, the core component of the Unix operating system.
In 1991, Torvalds was a graduate student at the University of Helsinki and
had bought himself a new personal computer (PC) based on Intel's 386 micro-
processor. Because he wanted to run Unix on his PC, he bought and installed
Minix, a version of Unix suitable for teaching that had been created by Andy
Tanenbaum at the Vrije Universiteit in Amsterdam. Inspired by the Minix soft-
ware, Torvalds started creating his own version of the Unix kernel for the PC.
B.4.9. Hal Abelson is a professor of electrical engineering and computer science at MIT. He is pas-
sionate about both open-source software and open courseware, and has been a champion for the
right to open access for publicly funded research publications. Abelson was one of the founders
of the Free Software Foundation and the Creative Commons movements. In addition, Abelson has
long believed in the potential for using computation as a conceptual framework in teaching. He is
the author of several influential textbooks and implemented the Logo programming language on
Apple II computers. Logo is widely regarded as one of the best programming languages for intro-
ducing computing to children. His pioneering work in education was recognized in 2012 by his
receiving the ACM SIGCSE Award for Outstanding Contributions to Computer Science Education.