Yoast License Manager.
1.6.0 2017-08-22 07:59 UTC
This library will take care of the following.
- Managing license related options
- Setting license key from a constant
- Obfuscasting (valid) license keys
- Remote license activation / deactivation
- Checking for plugin or theme updates
A sample plugin is included, have a look at its source.
A sample theme
functions.php file is included, have a look here.