Well, I think there is a general "personal use" clause in the copyright laws. I am no expert on copyright laws, but I believe the general idea is that the folks working on MorphOS don't want other OS's to benefit from their work.

About MacOS, you're a little mistaken, Apple is quite defensive over Aqua (their "window skin" so to speak). Let's just say I'm glad that I wasn't the guy who uploaded the VisualPrefs skin to the AmiNet that looked simular to Aqua... <shudders>