The Free On-line Dictionary of Computing (30 December 2018):
user interface copyright
There have been several attempts, mostly by big US software
companies, to enforce patents and copyright on user
interfaces. Such legal action aims to restrict the use of
certain command languages or graphical user interfaces to
products from one software supplier. This is undesirable
because it either forces users to buy software from the
company whose interface they have learned or to learn more
than one interface. An analogy is often drawn with the user
interface of a car - the arrangement of pedals and steering
wheel etc. If each car manufacturer was forced to use a
different interface this would be very bad for car users.
Following a non-jury trial, which began in early January 1987,
a federal judge ruled on 1990-06-28 that keyboard commands and
on-screen images produced by Lotus Development Corporation's
popular 1-2-3spreadsheet are protected by copyright.
Paperback Software International and subcontractor
Stephenson Software Ltd. who lost the case, argued that the
copyright applies only to the inner workings of the software.
US District Judge Robert Keeton wrote that "The user interface
of 1-2-3 is its most unique element and is the aspect that has
made 1-2-3 so popular. That defendants went to such trouble
to copy that element is a testament to its substantiality".
Defence attorneys had argued that the Lotus commands
represented "instructions for a machine rather than the
expression of an idea".
Soon after this decision, on 1990-07-02, Lotus sued Borland
International and the Santa Cruz Operation for producing
spreadsheets (Quattro, Quattro Pro and SCO Professional)
whose interfaces could be configured to look like 1-2-3's.