"The BSD license is very simple and therefore short. Its only condition is that people must mention the name of the author if they incorporate the software in their own programs. All other use and redistribution is permitted, including for commercial purposes. It is popular among authors who desire to have their work used by the largest number of people and who do not object to others making money from their software. The operating systems FreeBSD and OpenBSD and the web server Apache are notable examples. A comparable license is the MIT license, in which the user indemnifies the author from any liability arising from the use. Software under the Artistic License may be used and redistributed without further restrictions. Modifying the software is also permitted, but modified versions may only be redistributed if the modifications are freely available to all. It is not permitted to sell software covered by the Artistic License, which is permitted by most other standard licenses. A notable example is the Perl interpreter. Public domain is strictly speaking not a license. It means that there is no copyright on the software whatsoever. Without restriction, the software can be used, distributed, modified and distributed by anyone, anywhere, anytime. There are no restrictions on commercial exploitation of public domain software, identification of the original author is not required, and the author yields all rights and does not restrict anything third parties do with the software. The author is not liable for damages."