Losing license when migrating from old to new readynas chassi

Since the licenses are attached to your NAS serial number, they don't transfer directly.  But ReadyNAS support should be able to give you what you need to transfer the licenses to the new NAS serial number.  Do keep in mind, though, that Netgear stopped supporting Milestone Arcus some time ago, so you are delaing with an older version of the software and may at some point have a problem with an OS update.  So you may want to start looking at alternatives.  I personally use Blue Iris on a PC with my NAS as the target for video backup.