I am pretty sure that the file server cannot run on a demo license. I have seen this before. The demo functionality is not full functionality. Can you not license the file and appserver proper?
For future reference. I just tested starting the application server with a fileserver on the same host using a demo-license. It works! ;-)
The message in the appserver.log may appear if the fileserver is not reachable by name from the appserver's host, which one can easily test. Also you may experience some problems with wrong exports, users or users.local-entries.