The latest release version 1.4 contains an extended API for usage of compsat as backend for our QBF solver Quantor. It also contains the decomposition code described in our paper Decomposing SAT Problems into Connected Components. For more information on SAT and our solvers see the solver section on our software page. The technical report The Evolution from Limmat to Nanosat may also be interesting.
We use a BSD style license. In essence, you can use and modify the sources as you like provided that you acknowledge the origin of the software. More details can be found in the COPYRIGHT file that comes with the sources.