The FreeBSD Documentation License is the license that covers the documentation for the FreeBSD operating system. Based on this license, the BSD Documentation License was created to contain terms more generic to most projects as well as reintroducing the 3rd clause the restricts the use of documentation for endorsement purposes (as shown in the 3-clause BSD License).
The Free Software Foundation classes this as a free documentation licence, stating that "This is a permissive non-copyleft free documentation license that is compatible with the GNU FDL."