The reason why it didn't work before was that if the 'ide7' cluster is enabled, an NPE is thrown in this case. Fabrizio Giudici, who has integrated World Wind into his blueMarine project sometime ago (click here to see it in action), was the one who provided me with the missing piece of this puzzle. I asked him to try to work out what my problem was, since he didn't have that problem in his application. He wrote today with, amongst others, these words:
Ten minutes ago I figured it out! blueMarine has all the platform clusters disable but "platform6": going by trial and error, I discovered that if "ide7" is enabled, the NPE is generated (on all platforms, Mac included)... looks like it prevents the loading of the dynamic libraries of JOGL.
Thanks Fabrizio! What this means, unfortunately, is that one cannot install a module containing World Wind into NetBeans IDE, because there 'ide7' must always be enabled. It's a very strange situation, but at least it is good to know that I can now integrate the cool World Wind functionality into a (non NetBeans IDE centric) NetBeans Platform application!