I have a script, and I sell it to some people. I need a way to make sure that my script won't work on any website that not in my clients list.
What is the best method to avoid making people from stealing my script?
I read about making a license key in the script, so any script without license won't work. However, there are many ways to generate a license key without taking my permission right?
All I need is to not activate any script in any domain name, unless I have it in my clients list.
There's a reason Adobe, Microsoft, and others don't over actively pursue pirates (not saying they don't, just not at epic, absolutism levels) - they make most of their money from business to business sales and support. A simple license and support structure is typically enough to posture yourself for profit from legitimate businesses and parties who want your product.
Technical protection is a losing battle if you're going to give anyone the code. That's why SaaS is so popular.