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