A copyright provides its holder the right to restrict unauthorized copying and reproduction of an original expression (i.e. literary work, movie, music, painting, software, mask work, etc.) Copyright, unlike patents, does not grant a monopoly right to the use of an invention or an idea, but merely the right to prevent others from copying your specific implementation or expression. Copyright should also not be confused with the form of intellectual property law called trademarks. Copyright also does not prohibit all forms of copying.
In the United States, the fair use clause of the Copyright Act allows copying and distribution under certain limited circumstances. Copyright law is controversial, with some seeing it as essential to prevent abuse, while others find it too restrictive. This has led to the concept of copyleft and alternative licences. (more...)