Enforcement of copyright is sometimes sporadic, and varies from place to place. As mentioned, Lucas encourages it within limits. Paramount (Star Trek, etc.) occasionally goes on spates of enforcing their copyright, perhaps halfheartedly. Marvel Comics is relentlessly ruthless. Keep in mind that there is a cerain amount of necessity in this. Hormel recently lost their copyright on SPAM, because it had been allowed to become so completely part of our common vernacular. Similar fates have befallen Xerox and Kleenex. There are precedents that if a company doesn't enforce and actively protect their own copyright, then the court doesn't feel that the copyright's protection is its responsibility, either. I don't like it either, but the long and short of it is, don't use copyrighted characters, unless you're willing to be forced to remove your work from any kind of public display or access. Lucasfilm stuff may be an exception, but who knows -- someday after Lucas passes on, his heir(s) may have different views on the matter.