CALSIM Water Resources Simulation Model 

     CALSIM is copyrighted by the State of California, Department of Water Resources. It is licensed under the GNU General Public License, version 2. This means it can be copied, distributed, and modified freely, but you may not restrict others in their ability to copy, distribute, and modify it. See the license below for more details.

http://www.fsf.org/copyleft/gpl.html