The CMT toolkit is licensed under GPL version 2.
As I understand it (I'm not a lawyer) this means that, once built, the CMT library may be used with non-GPL'd applications as long as it is built and loaded using the standard LADSPA dynamic-linking approach without modification. In my opinion this is a good thing for the toolkit, if not for the GPL.
The above may not be correct when built against the LGPL version of the ladpsa.h header file, but it is certainly the way we would like things to be. See the LADPSA license for further details.