Groundhog Copyright © 2014 German Molina (www.IGD.cl), Sergio Vera (School of Engineering, Pontificia Universidad Católica de Chile) & Waldo Bustamante (School of Architecture, Pontificia Universidad Católica de Chile).
Groundhog is distributed under GNU General Public License v3.0.
Among other things, that means that you can use it as much as you want for any purpose. You can also modify Groundhog in every way you want, but you are not allowed to sell any modified copy of it. In fact, any modified copy of Groundhog should also be licensed under the GNU GPLv3.
Forking, copying and modifying Groundhog is allowed and encouraged. However, if you want new features, please add them to the main project instead of starting a whole new divergent one. This will help Groundhog grow to its full potential which, I believe, is better for everyone.