Must I credit others' published research when using it in a proprietary product, if doing so would be bad for business?
Since business is on your mind, before ethics, you should first check whether there are any legal restrictions on the use of the published research, or obligations arising from such use, issues that may depend on the applicable laws of some specific country. For example, it may be the case that you may not need consent to use the research results, since they have been openly published, but you may have some financial obligations if you are to use it for profit (and not necessarily towards only the research team), patent or no patent. So make certain where you stand.

As for ethics: it is rare for businesses to credit researchers. Instead they usually contract them either for royalties or to secure further development, if there is such potential, and not leave it to fall into the hands of competitors. "Credit due" may be one of the currencies in academia, but "money" is the currency that businesses understand. 

By contacting and maybe contracting the research team (after doing your legal due diligence first), you may even be able to secure such exclusive use of their results, or some even more efficient version of them. Again, this will depend on the legal framework applicable.