This article explains how the Server Express licensing works when using a clustered file system.
Problem:
Within a clustered file system, when the host falls over, will the Server Express runtime license broker (aslmf) automatically recover?
Resolution:
At the time this article was written (March 2009) Server Express is not cluster aware so if you fail-over to another machine, some interaction is required to ensure the licence database (mflmfdb) is licensed. This can be automated to a point by using aslmdbrecover, then apptrack in batch mode to populate the database.