It all depends on the situation and whether or not an agreement was met by the original copyright holder and the brokerage that the violating product was in.
I know that here, if an  item is removed for copyright violation, you will be told 1. Whether or not you need to delete it from your hard drive, 2. Whether or not other pieces of the vendor's work you may have are in violation.
There have been times (I don't recall if any of them involved Renderosity products, but, they happened) when the copyright holder has ok'd the further use of the purchased product OR a refund.  Both DAZ and Smith Micro have ok'd use in that instance, but it's always a case-by-case basis, and it's always up to the original copyright holder. 

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Knowledge is knowing a tomato is a fruit. Wisdom is not putting it into a fruit salad.