Completely wrong. Myrthos means that it is so complicated that no-one could work with it. Someone has explained it once, a long time ago.
This does not mean it uses or doesn't use licensed material - we simply don't know.
All I know - the public knows - is that it was never published because it was too heavy and complex.
That's the same reason Gothic I never had a Mod-Kit released, from what I've heard.
(Though Gothic II got a release of a SDK/Mod-Kit, in German).
