The Apache License is permissive; unlike copyleft licenses, it does not require a derivative work of the software, or modifications to the original, to be distributed using the same license. It still requires application of the same license to all unmodified parts. In every licensed file, original copyright, patent, trademark, and attribution notices must be preserved (excluding notices that do not pertain to any part of the derivative works). In every licensed file changed, a notification must be added stating that changes have been made to that file.