Untouchable local server

We have a software that needs a connection to our servers for license management purposes. Now we have a new customer who wants to use our software on systems that don’t have access to internet. So I was thinking about setting up a local server in their private network. Is it a good way? What are the flaws of this approach? Is it possible that they copy our server data and use it somewhere else? In other words can they clone our server? If they can what’s the solution? Can I in some way use a TPM to prevent cloning?