The Historical Permission Notice and Disclaimer is an open source license, approved by the Open Source Initiative (OSI). It is unique among the OSI's licenses because of the choices it allows in its construction; it lets you pick anywhere from 0-2 warranty disclaimers, whether you want to prohibit your publicity of the software derivatives (like in the BSD License), and other spelling and grammar options. Besides this, the license can be almost functionally identical to the new 3-clause BSD License (if the option for the no-promotion clause is exercised), or the MIT License (if the option for the no-promotion clause is not exercised).