Copyright law governs the sale and distribution of "intellectual property" such as books, articles, musical compositions, and computer programs.
Phil Albert wrote, "... copyright laws give an author exclusive rights to make derivative works."  (Note that this quotation is a fair use of a copyrighted work!)
- copyright - compare patent, trademark
- copyright infringement
- derivative work
- end-user licenses
- open-source software, open-source licenses, open-source licensed software
- viral software, "viral nature", "copyleft"
- the General Public License, "free software" - Free Software Foundation
- proprietary software
- shrink-wrap contract
- reverse engineering