A staff of five, for example, using three software programs, must buy 15 licenses. Of course, this strict view is biased, just like the IRS viewpoint detailed above. Fortunately, the software lawyers are usually busy chasing blatant license violations, such as businesses where copying software is commonplace. I won't say what you must do. As a practical and honest businessman, however, I can discuss considerations for your decisions.
People create software programs much as they write books or produce movies.
It is a blend of intellectual inspiration and hard work turning inspiration into reality. In our society, we believe that people are entitled to the fruits of their labors. In short, a programmer is entitled to payment for using his software. When I go home at night, no one is using my word processor in the office. This is a situation where ethically you might be right, but you should be prepared to be challenged by the software lawyers.