"An independent software author owns the copyright on the program. This enables the author to regulate the copying, using and adapting of the program. The author must specify conditions of use in a license. Several standard licenses are possible, including exclusive rights, the GNU General Public License, the BSD license, the Artistic License and public domain. An author has the right to restrict copying, modification and distribution, and may authorise others to distribute software, with or without charge. The conditions of this authorisation are specified in the license. A license can be specific for one recipient, as is often the case with custom-made applications, or written in a generic way, like most standard software sold in stores or available for download on the Internet. If an author desires to sell software, a carefully drafted license is essential. If an author desires to give software freely, a license is still required to specify the conditions under which users may execute and distribute the software. The two options are to use a standard license or write one’s own."