There are two reasons for having the models be open source:
Widest possible use: We want to ensure the maximum benefit to people and the planet resulting from our models. The best way to ensure their widespread use is to make them free. Making this argument even stronger, the software that hosts the models is also free and open-source thus removing a key barrier of entry to those who want to join the CAC Community.
Building a collective knowledge base: If the models were “closed source” and proprietary (even if we were to give them away for free), there would be little incentive for members of our community to enhance the models and contribute their knowledge into the ecosystem. By providing the models using an MIT license, we encourage not only the free use of the models, but also we encourage members of our community to enhance the models and contribute those enhancements back to central repository thus helping all other members of our community. As has been demonstrated at ESA, digital models can be an extremely effective way of sharing knowledge across a large number of projects.