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No, making money through usury is unethical. At least if we are going by typical biblical ethics, otherwise all we are left with is personal opinion. In which case, screw your ethics.
The Bible has a much wider interpretation of "usury." Religious law, both Jewish and Christian, prohibits lending money with interest -- that's usury. Which pretty much precludes "making money by having money" (though there's nothing there about deflationary currencies, which could be seen as making the holder wealthier).
No.
Usury is usury. That is lending money and getting more money back with no further effort on your part. That says nothing about any other form of business.