The Energy Policy Simulator (EPS) is released under the GNU General Public License version 3 (GPLv3) or any later version and is free and open-source software. The full license text is available in English and in many other languages. A simple, easy-to-read, unofficial guide to the main attributes of the GPLv3 is available here.
Note that this license applies to the EPS, not to Vensim. Vensim is commercial software and is owned by Ventana Systems. We recommend the use of Vensim Model Reader to run the model. You may change the input data using Microsoft Excel or any program capable of reading Excel files, such as Open Office.