I've built a small tool that I distributed as "free for personal use, contact me for a commercial license", without technical enforcement, not even a nag screen. I made one (1) sale, despite receiving e-mails from several people thanking me that they're happily using it at work, and that sale was to a company who wanted customization, and only ended up actually paying the invoice when they asked for another round of…
This is a really important point. Small companies I've worked at generally have had sensible and manageable procurement processes, but big companies have sometimes had mind bogglingly labyrinthine processes even for small purchases. There was once I had to raise an "Approval To Spend" and "on-board" a new vendor, and as far as I could tell the process changed 3 times while I was going through the "process", although I'm not completely sure because while everyone was telling me I had to go through "the process" no-one seemed completely sure what the process was, including those responsible for "the process". All very Kafkaesque. Anyway, it all comes down to your target market - if it is individuals you won't face this problem, but if it is businesses you will face the problem on a scale according to the size of business.