It is not permitted (nor technically possible -- our licensing system won't allow it) to simultaneously *use* the same license one more than one server at a time.
But if you can set it up such that your second server remains dormant until you need it, and then just move the license over at that time before bringing the new machine up, that's essentially the poor-man's equivalent of running a 2-node cluster with something like DRBD+pacemaker for high availability, which is is perfectly reasonable. And if it's setup right, your license is never in use on more than one machine at a time, so it's well within the licensing terms.
Actually implementing this is up to you (eg: it's not something we would provide technical support for, or assistance with) but the general idea would look something like:
1. Install CC on the secondary machine
2. Stop CC (/etc/init.d/centovacast stop) and remove its init scripts (eg on Debian: update-rc.d -f centovacast remove) so that it doesn't automatically start up at boot.
3. Temporarily disable its cron job by moving /etc/cron.d/centovacast to a temporary location.
4. Setup some kind of filesystem and database synchronization between the "live" server and the secondary machine.
And then to perform a failover, do the following on the secondary machine:
1. Reissue the license in your client area at centova.com.
2. Perform any updates in the database or on the filesystem -- eg: if you're replicating your filesystem/database, you'll need to change all the IP addresses in the DB and in the *.conf files on disk to match those on the slave machine. If you're only replicating your media, you'll need to perform a media library update to pull in any media that was added since the last time the secondary was active. The replication and updates of this nature are the hard parts, really, and are left as an exercise for the reader.
3. Move /etc/cron.d/centovacast back into place
4. Start CC (/etc/init.d/centovacast start)
The one thing you'll want to be careful of, however, is failing over too frequently. If you exceed a certain threshold, our licensing system will detect that you're reissuing your license back and forth between the same two servers over and over, and it'll assume you're trying to "beat the system" to use the same license on two servers. If that happens, further reissuances will be blocked for a period of time, which would be a bad thing to happen during a server outage.
In a nutshell, though, as long as no two servers are live at the same time with the same license, you can move around your licenses as needed and not run afoul of the licensing terms.