The simplest solution I'm aware of is Software as a Service. I run a few SaaS products and make a fairly good living. People can use my software as much as th

The simplest solution I'm aware of is Software as a Service. I run a few SaaS products and make a fairly good living. People can use my software as much as they like, provided they pay, and provided it's running on one of my machines. So long as they never get their hands on a copy of the thing, there's nothing for them to copy.