Hello,
I have 9 years of experience in developing provisioning modules, addons, registrar modules for WHMCS.
I have created many provisioning modules, that can provision accounts via API. I can make this for you.
I follow PSR coding practices and create a readable and reusablecode. I use inbuilt WHMCS functions and DBAL functions, which makes the code run in future WHMCS/php version upgrades as well.
I specialise in WHMCS, and mostly do WHMCS based projects. You can view my profile here: https://www.freelancer.com/u/phpizephing
I have created VPM modules earlier, that uses OpenVPN and freeradius.
The licensing can be done using WHMCS License manager module. To use it effectively, you will need to encode this vpn module with ionCube encoder. I have experience in both WHMCS License Manager & ionCube.
Regards