Gosling Emacs was an Emacs

Emacs

Emacs is a class of text editors, usually characterized by their extensibility. GNU Emacs has over 1,000 commands. It also allows the user to combine these commands into macros to automate work.Development began in the mid-1970s and continues actively...

 implementation written in 1981 by James Gosling

James Gosling

James A. Gosling, OC is a computer scientist, best known as the father of the Java programming language.-Education and career:In 1977, Gosling received a B.Sc in Computer Science from the University of Calgary...

 in C

C (programming language)

C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

. Its extension language, Mocklisp

Mocklisp

Mocklisp is the extension language of Gosling Emacs. While resembling Lisp in many ways, it is semantically quite different. Richard Stallman characterized it as a programming language that "looks syntactically like Lisp, but didn't have the data structures of Lisp. So programs were not data, and...

, has a syntax that appears similar to Lisp

Lisp programming language

Lisp is a family of computer programming languages with a long history and a distinctive, fully parenthesized syntax. Originally specified in 1958, Lisp is the second-oldest high-level programming language in widespread use today; only Fortran is older...

, but Mocklisp does not have lists or any other structured datatypes. Gosling initially allowed Gosling Emacs to be redistributed with no formal restrictions, but later sold it to UniPress

Unipress

Institute of High Pressure Physics, also known as Unipress is a scientific institute founded in 1972 by the Polish Academy of Sciences .-The main fields of activity:* Biological materials...

.

Gosling Emacs was especially noteworthy because of the effective redisplay code, which used a dynamic programming

Dynamic programming

In mathematics and computer science, dynamic programming is a method for solving complex problems by breaking them down into simpler subproblems. It is applicable to problems exhibiting the properties of overlapping subproblems which are only slightly smaller and optimal substructure...

 technique to solve the classical string-to-string correction problem

String-to-string correction problem

The string-to-string correction problem refers to the minimum number of edit operations necessary to change one string into another. A single edit operation may be changing a single symbol of the string into another, deleting, or inserting a symbol...

. The algorithm was quite sophisticated; that section of the source was headed by a skull-and-crossbones in ASCII art

ASCII art

ASCII art is a graphic design technique that uses computers for presentation and consists of pictures pieced together from the 95 printable characters defined by the ASCII Standard from 1963 and ASCII compliant character sets with proprietary extended characters...

, warning would-be improvers that even if they thought they understood how the display code worked, they probably did not.

Since Gosling had permitted its unrestricted redistribution, Richard Stallman

Richard Stallman

Richard Matthew Stallman , often shortened to rms,"'Richard Stallman' is just my mundane name; you can call me 'rms'"|last= Stallman|first= Richard|date= N.D.|work=Richard Stallman's homepage...

 used some Gosling Emacs code in the initial version of GNU Emacs. UniPress began selling Gosling Emacs (which it renamed Unipress Emacs) as a proprietary

Proprietary software

Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...

 product, and, controversially, asked Stallman to stop distributing Gosling Emacs source code. UniPress never took legal action against Stallman or his nascent Free Software Foundation

Free Software Foundation

The Free Software Foundation is a non-profit corporation founded by Richard Stallman on 4 October 1985 to support the free software movement, a copyleft-based movement which aims to promote the universal freedom to create, distribute and modify computer software...

, believing "hobbyists and academics could never produce an Emacs that could compete" with their product. All Gosling Emacs code was removed from GNU Emacs by version 16.56, with the possible exception of a few particularly hairy sections of the display code. The latest versions of GNU Emacs (as of August 2004) do not feature the skull-and-crossbones warning.