How to protect our extension with serial number or other way

[hgzica]

How to protect our extension with serial number or other way?

Can I obfuscate the files or parts of the code?

Any suggestion?

[eCommerce Core]

There is a unique license key generated for each purchased license. It is deactivated if order is canceled or marked as fraud.
Customer will not be able to download or install extension any longer.

Unfortunately, there is no way to deactivate extension on customers' site. 

As a developer/vendor on the marketplace, you can see the status of the order.