The software license under which software from the Apache Foundation is distributed is a distinctive part of the Apache HTTP Server's history and presence in the open source software community. The Apache License allows for the distribution of both open and closed source derivatives of the source code.
The Free Software Foundation does not consider the Apache License to be compatible with version 2 of the GPL in that software licensed under the Apache License cannot be integrated with software that is distributed under the GPL:
This is a free software license but it is incompatible with the GPL. The Apache Software License is incompatible with the GPL because it has a specific requirement that is not in the GPL: it has certain patent termination cases that the GPL does not require. We don't think those patent termination cases are inherently a bad idea, but nonetheless they are incompatible with the GNU GPL.
However, version 3 of the GPL includes a provision (Section 7e) which allows it to be compatible with licenses that have patent retaliation clauses, including the Apache License.
The name Apache is a registered trademark and may only be used with the trademark holder's express permission.