knowledge-based protein-protein interface design code see Clark and van Vlijmen Proteins. 2008 Mar;70(4):1540-50. A knowledge-based forcefield for protein-protein interface design. http://www.ncbi.nlm.nih.gov/pubmed/17910054  please see example_1I9R/README for an example the parameter files are in example_1I9R/gofrfiles/  The code was attached to the above article with the GPLv2 http://www.gnu.org/licenses/gpl-2.0.html