RStan (package rstan) are licensed under GPLv3 (http://www.gnu.org/copyleft/gpl.html)

Other sources distributed with RStan are under different licenses: 

1. Stan code (in folder include/stansrc) included in RStan
   are licensed under new BSD (http://www.opensource.org/licenses/BSD-3-Clause).

2. Part of boost library (in folder include/stanlib) distributed with RStan is 
   under the Boost Software License version 1.0 (http://www.opensource.org/licenses/BSL-1.0) 

   


