Halachic question regarding the source of funds

Person "A" gave person "B" a loan without interest or linkage.
Person "B" wants to repay part of the loan to person "A" through person "C" who owes person "B" money.
The problem is that person "A" knows that the source of the financial obligation between person "C" and person "B" is not kosher, i.e. person "C" owes person "B" money because of a service that person "B" provided to person "C". The service, for this purpose, is an infringement of intellectual property, for this purpose the sale of a copied book.

Is person "A" allowed to receive the money directly from person "C"?
If he has already received it, what should he do?