Well, I'm still not much further on. Do you want the processing to run on the POS or the server?
Running on the POSPerhaps NFS or Samba sharing the files to the POS. You have to consider security so no-one else can pick it up.
Running on the serverThe POS can send a connection to the server to do the work then return. You still have to consider security though on how you authenticate the incoming connection.
Are you worried about the POS being physically removed or just hacked? Either way, it might still be possible to access the code & data by mimicking what the POS does routinely.
This could be a major design project in the making, but you know your business far better than us, so you need to clarify what you want to do and then we can see how we can help. What does your POS do so far?
Robin