Registring FreePBX

I was looking information about how to register FreePBX, and I find that the only FreePBX that is possible to register is the one that we install using Distro.
But I find in Wiki this information: "Non-FreePBX Distro systems, such as PIAF, do not support FreePBX commercial modules at the time of installation. You will need to install a few packages and a FreePBX module to register your system. Please follow the guide below to enable support for FreePBX commercial modules."
Here we can see that is possible to register FreePBX so my question is: can we register FreePBX that we install manually or not? Can we buy Comercial modules or not, if we install it manually?
Thank you very much for your time and attention

You can only register Distro systems. Everything else is unsupported for registration. Commercial Modules are also only supported on FreePBX Distro systems.

So, if I have a Centos server and want to add freepbx functionality to it, I cannot use a commercial modules?

You have to install the Freepbx distro if you want to use commercial modules.