The Free On-line Dictionary of Computing (30 December 2018):

software law
law

    Software may, under various circumstances and in
   various countries, be restricted by patent or copyright or
   both.  Most commercial software is sold under some kind of
   software license.

   A patent normally covers the design of something with a
   function such as a machine or process.  Copyright restricts
   the right to make and distribute copies of something written
   or recorded, such as a song or a book of recipies.  Software
   has both these aspects - it embodies functional design in the
   algorithms and data structures it uses and it could also be
   considered as a recording which can be copied and "performed"
   (run).

   "Look and feel" lawsuits attempt to monopolize well-known
   command languages; some have succeeded.  Copyrights on
   command languages enforce gratuitous incompatibility, close
   opportunities for competition, and stifle incremental
   improvements.

   Software patents are even more dangerous; they make every
   design decision in the development of a program carry a risk
   of a lawsuit, with draconian pretrial seizure.  It is
   difficult and expensive to find out whether the techniques you
   consider using are patented; it is impossible to find out
   whether they will be patented in the future.

   The proper use of copyright is to prevent software piracy
   - unauthorised duplication of software.  This is completely
   different from copying the idea behind the program in the same
   way that photocopying a book differs from writing another book
   on the same subject.

   Usenet newsgroup: news:misc.legal.computing.

   ["The Software Developer's and Marketer's Legal Companion",
   Gene K. Landy, 1993, AW, 0-201-62276-9].

   (1994-11-16)