Plugin trial and license check. How to do ?

This question is for developers, who are seling plugins.
How to check trial period and license?
Any practical aproach or library you can suggest?

Hi Cesar,

Please visit here for free license plugin.

It also have source code with instruction, which can help you.

Is there an updated guide on how to do this? the previous link is broken. I also need to learn how to make my plugin licensed and not sure where to start.

Thanks