A post on the Macenterprise mailing list and an article at TidBITS take note of this licensing change, which now would seem to explicitly permit the use of multiple instances of Mac OS X Server on a single Apple machine. With this green light, applications like the in-early-beta Parallels Server and the unannounced but surely-in-progress VMware equivalent could provide multiple instances of OS X Server along with Linux or Windows VMs, all on the same box. Depending on how your network services are set up, this could be a big help in selling X Server into your organization.
We'll keep an eye on both Parallels and VMware for future announcements in server virtualization. Exciting times!
via Adam Engst/twitter. Thanks to everyone else who sent this in.