Open Source & Derivative Works
WordPress & the GPL
ProCD v. Zeidenberg
USL v. BSDi
Shrink Wrap License
MS Community License
MS Permissive License
The BSD licenses are a set of very permissive free software licenses that allow use of the licensed code in both FLOSS and proprietary works. In general, the BSD licenses have very few restrictions as compared to the GPL or other copyleft licenses, put the licensed material in a situation which is closer towards public domain.
BSD licenses have their origin in the Berkeley Software Distribution, a UNIX-like operating system written at the University of California, Berkeley, and which lives on today as the various BSD operating systems.
Since its birth, there have been many variations on the original BSD license, which include various modifications to the license's terms and conditions. Possibly the most important difference between the variants is that the original "4 clause" license contained an advertising clause which required acknowledging the software in all advertising materials. The advertising clause is incompatible with the GPL, and hence some revised versions of this license removed the clause in order to achieve compatibility.
Finally, several versions of the license have been verified by the Open Source Initiative as being compliant with the criteria of the Open Source Definition.