[Bf-cycles] C++ API and the GPL

[Dan Eicher]

Been doing research on the interwebs and have come to the conclusion
it's not possible for a proprietary renderer to use the the C++ api.

The only way for this to work would be something like
http://www.gnu.org/licenses/gpl-faq.html#LinkingOverControlledInterface.

Just thought I'd throw this out there since I'm sure it'll come up
again now that the api is being actively used in trunk.

Dan