Berkeley Software Distribution licenses

The BSD family of licenses are considered "Permissive licenses," meaning users are granted complete control over software that is derived from the original BSD Licensed software.

In this way BSD licenses are considered very close to simply placing software in the Public domain.

This license model differs fundamentally from other open source licenses such as the GNU General Public License, which requires derivative software to have its source code freely available upon request, and derivative works placed under the same license.