Sam Williams, Free as in Freedom (2002) — Chapter 8… (2002)
“ The difference between protecting a program under copyright and protecting a program under software patents is subtle but significant. In the case of copyright, a software creator can restrict duplication of the source code but not duplication of the idea or functionality that the source code addresses. In other words, if a developer chooses not to use a software program under the original developer's terms, that second developer is still free to reverse-engineer the program—i.e., duplicate the software program's functionality by rewriting the source code from scratch. ”
