Website checker,

written in PHP5, based on Zeta Components
allows you to add your own tests & benchmarks extending the exsisting tests. 
GNU Affero GPL'd.

Feel free to fork it on github : https://github.com/ronanguilloux/rgWebCheck

License compatibility : 
The Apache Zeta Components are now under Apache License, Version 2.0.
The Apache Software Foundation and the Free Software Foundation (FSF) 
agree that the Apache License 2.0 is a free software license, 
compatible with version 3 of the GNU General Public License (GPL).
You can read more about that at http://www.gnu.org/licenses/license-list.html#apache2