This 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 deriviatives (like in the BSD License), and other spelling and grammar options. Becides 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 not exercised).

Variants of this license are in use primarily in older software, including the original BSD kernel, developed by IBM, Intel and others. Today, it is most popular to choose either the new 3-clause BSD License or the MIT License to meet the licensing needs of the developer.

This is the only OSI-certified license (excluding the public domain) that can lack a disclaimer of warranty. The Free Software Foundation has not yet recognized this license as a free software license; this is probably due to its lack of use in today's programming, and not due to the license itself.

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