Free to develope the plugin?

Yeah sure.

It is probably better to create your own addon for it if you want. We can add necessary filters or action hooks if you need.

We continuously improve this plugin and release security updates (if needed). Making your own addon means, that your customers will be able to upgrade the core plugin and they will have access to an updated plugin all the time. Otherwise if you create your own version it will get outdated sooner or later.

Yes, thanks. I will try to integrate without modify the core plugin.