http://www.davismccownlaw.com/articles/a-ip.htm

Copyright protection is limited to the *expression* of an idea. Copyrights can not protect raw ideas removed from their expression. For instance, a programmer could write a computer program which forecasts the weather based on current weather information. Another programmer could see the program and decide to create and sell her own version. So long as she does not copy the actual code created by the first programmer, or the *''look and feel'' of the program itself*, the second programmer is free to use the ''idea'' of a weather forecasting program to create

http://www.law.uchicago.edu/news/posner-r-plagiarism...

The Truth About Plagiarism
It's usually a minor offense and can have social value
Richard A. Posner
Newsday (New York)
May 18, 2003

Richard A. Posner is a judge on the U.S. Court of Appeals for the Seventh Circuit, based in Chicago, and a senior lecturer at the University of Chicago Law School.

unlike real theft, it is not a crime. If a thief steals your car, you are out the market value of the car; but if a writer copies material from a book you wrote, you don't have to replace the book

There is a danger of overkill. Plagiarism can be a form of fraud, but it is no accident that, unlike real theft, it is not a crime. If a thief steals your car, you are out the market value of the car; but if a writer copies material from a book you wrote, you don't have to replace the book.