The next least restrictive kind of license grants unrestricted rights to copy, use, modify, and redistribute modified copies as long as a copy of the copyright and license terms is retained in all modified versions, and an acknowledgment is made in advertising or documentation associated with the package. Grantee has to give up the right to sue the maintainers.
The original BSD license is the best-known license of this kind. Among parts of the free-software culture that trace their lineages back to BSD Unix, this license is used even on a lot of free software that was written thousands of miles from Berkeley.
It is also not uncommon to find minor variants of the BSD license that change the copyright holder and omit the advertising requirement (making it effectively equivalent to the MIT license). Note that in mid-1999 the Office of Technology Transfer of the University of California rescinded the advertising clause in the BSD license. So the license on the BSD software has been relaxed in exactly this way. Should you choose the BSD approach, we strongly recommend that you use the new license (without advertising clause) rather than the old. That requirement was dropped because it led to significant legal and procedural complications over what constituted advertising.
You can find a BSD license template at the OSI site.
