This used to be much more common. I worked on a product in 2004 that licensed a library around providing a nice SDK for different payment processors. Effectively making it super simple to switch or route payments to different processing gateways.

We paid on a per domain basis and also paid a yearly maintenance fee to get updates. Nothing stopped us from just using the library in ways that violated the license but we didn’t. The threat of lawsuit is an effective deterrent if the ethical concerns aren’t.

In my experience for B2B the people that are going to steal from you were never going to pay anyways.