No one in the history of commerce has been able to prevent dishonest businessmen. Or, for that matter, dishonest customers or governments. We (collectively) get by because most people are pretty honest (whether businessmen, customers, government reps, etc.) and we do after the fact penalties (that is, lawsuits) for the dishonest ones that are found.
There are two ways you can go:
- Free distribution, asking business/commercial users to pay
- Some kind of encrypted, DRM distribution with unique watermarks per copy
The first leaves you vulnerable to cheaters and to those whose definition of "businessmen" differs from your own. For instance, I infer you want to allow free distribution to students. Does that include those who are charging for teaching a class? You can think of all sorts of grey areas if you try. You won't prevent anyone from violating your copyright terms, but you may be able to recover damages or impose penalties via a lawsuit. Note that a lawsuit requires effort, expense, effort, and has no guarantee of success.
The second involves a lot of overhead, effort, and expense on your part. Further, the true cheaters will probably be able to get past your efforts at restriction, so your efforts won't be very effective anyway. However, that does allow you to trace the cheaters and makes it somewhat easier to show violations should you go to the expense and effort of a lawsuit.