license check in plugin

You can use a strategy referred to as “freemium” where you distribute a free version of your technology but require users to pay for an enhanced version (often with more features and support).

To implement the paid license is a topic more complicated and diverse than can be answered in-depth here. But the short & sweet of it is you have a separate website with users, of which each paid copy of your technology is a member of and must login to in order to update.