The FreeBSD project aims to develop a comprehensive BSD-licensed operating system that will allow users of the system to manufacture unrestricted derivatives or other licensing requirements. We invite and appreciate the contribution of changes and additions under the BSD license to two clauses and encourage the acceptance of this license by other open source projects. The use of the BSD license is the key to promoting the introduction of advanced operating system technology and has been instrumental in the widespread use of new technologies on many remarkable occasions. This version allows unlimited replay for all uses, as long as copyrights and licence warranty exclusions are maintained. The license also contains a clause limiting the use of contributors` names for the approval of a derivative work without specific permission. With one exception, no BSD-licensed component can be replaced by other licensed software. Instead, we recommend that FreeBSD and third-party developers request the re-licensing or implementation of critical components under the BSD license. This would make it easier to integrate them into the FreeBSD operating system.  This handling of patent litigation renders v2.0 incompatible with the GNU General Public License described in the next chapter.
See www.apache.org/licenses/GPL-compatibility.html. Apache`s license, v2.0, works primarily like MIT, BSD and Apache License, v1.1, with some additional benefits. First, it specifies that the licensing of Derivative Works under other licences is permitted as long as the conditions of the Apache licence, v2.0, are met. This is implicit, but is not explicitly specified in the MIT and BSD licenses. Second, Apache`s license, v2.0, offers clearly marked pathways for open development and unopened development of the code under which it is allowed. With the establishment of the contribution, a licensee agrees that this supplement to the work should be licensed under the same open conditions as those applicable to the original work. Especially for dynamic and well-organized open developments like Apache, this is probably a common result for changes. But there is no obligation to make a contribution: licensees can take their work as a writer and license it under another license. While this approach does not address the tension between open development and closed software development, it at least specifies which options are clear.