GNU ZRTP4J is distributed under the terms of the GNU General Public License 
with the following clarification and special exception. 

    Linking this library statically or dynamically with other modules is making
    a combined work based on this library. Thus, the terms and conditions of 
    the GNU General Public License cover the whole combination.

    As a special exception, the copyright holders of this library give you 
    permission to link this library with independent modules to produce an 
    executable, regardless of the license terms of these independent modules, 
    and to copy and distribute the resulting executable under terms of your
    choice, provided that you also meet, for each linked independent module,
    the terms and conditions of the license of that module. An independent 
    module is a module which is not derived from or based on this library. If 
    you modify this library, you may extend this exception to your version of 
    the library, but you are not obligated to do so. If you do not wish to do
    so, delete this exception statement from your version.

This exception covers only the modules in the gnu.java.* packages. This
exception is in effect even if it is not stated explicitly in the source files.
Modules in the org.bouncycastle.* packages are not affected by this exception, 
they use the original bouncycastle license (license file in this folder).

As such, ZRTP4J can be used to run, create and distribute a large class of
applications.