Modern Rockwell licenses require FactoryTalk Activation Manager (FTAM) which must phone home or use a hosted license server. If your plant is air-gapped for security (e.g., defense or critical infrastructure), FTAM becomes a nightmare. The activation is offline, permanent, and does not expire. Once the master disk is verified and you generate your LICENSE.DAT file, that PC remains licensed forever.
In older Rockwell Software ecosystems, a "Master Disk" was a physical floppy disk containing a hidden activation file.