THSim v4.0.3 is free of charge for researchers and students, for commercial use please contact the author. However, if you wish to publish results obtained with THSim v4.0.3, you should cite the following paper:
Vogt, P. (2003). THSim v3.2: The Talking Heads simulation tool. In W. Banzhaf and T. Christaller and P. Dittrich and J. T. Kim and J. Ziegler (Eds.) Proceedings of the 7th European Conference on Artificial Life, ECAL 2003. (the paper is included in the package)