As noted, Renderosity vendors do not need to specify any licensing restrictions.  These are spelled out in full detail by the included Renderosity license.txt file included with every purchased item in the MP.

Of course, as muralist notes, if somehow an item in the MP uses a previously copyrighted or trademarked design without the originators permission, then it breaks saleability policy and will more than likely be removed.  The Alien, Darth Vader, Wookies, BattleStar Galactica, and so on are usually covered by the owner of the design under copyright/trademark laws.  Note that a Darth Vader 'character set' is actually available - for FREE for NON-commercial use.  That, for the most part, is within terms (though some gungho owners even go after these - on rare occasions).

C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, you blow your whole leg off.

 -- Bjarne Stroustrup

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