BSD is a free software license deriving from the free unix operating system: BSD. It is one of the least restrictive open source licenses, along with the MIT License.
The only requirement for using BSD code is that the original authors of the code must be attributed.
In some of the early versions of BSD, a controversial clause required that advertising for software that used BSD code must mention UC Berkeley, however a revision of the BSD eliminated this clause and it is no longer in common use.
Many commercial products including Windows and Mac OS X include code that is licensed under the terms of the BSD License.
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