How to backup a license server?

About the only thing that might be of use is to make a disk image copy of the primary disk.  On a physical machine the license store is dependent on the motherboard and hard disk IDs.  If you fry your motherboard and get it replaced, or if you fry the hard disk and then lay the disk image down on a replacement disk (in that same machine), you should still be good to go.  One of the two required IDs is still valid and the licenses will still work.

If that happens, and you're a conservative kind of guy, you could then deactivate all licenses on the machine, reformat the disk, reload the OS and the License Manager, and reactivate your licenses.  In this way, by creating a completely new license store on the machine, you cause that license store to depend on the new set of IDs.