From the Leopard Server License:
This License allows you to install and use one copy of the Mac OS X Server software (the "Mac OS X Server Software") on a single Apple-labeled computer. You may also install and use other copies of Mac OS X Server Software on the same Apple-labeled computer, provided that you acquire an individual and valid license from Apple for each of these other copies of Mac OS X Server Software.
While this change only applies to Leopard Server, the implications are that it will be easily possible for the 10.5 client OSX to run as well. Paralles and VMware are the two main vendors of virtualization solutions on the Mac platform and are both involved in this new development. While Parallels market is mostly Macintosh machines, VMWare also runs on Windows or Linux.
More from Tidbits who got a chance to talk to people at Parallels and VMWare:
Ben Rudolph, Director of Corporate Communications for Parallels, told me, "Enabling Leopard Server to run in a virtual machine may take some time, but we’re working closely with Apple on it and will make it public as quickly as possible."
Pat Lee, Senior Product Manager at VMware, concurred, saying "We applaud Apple for the exciting licensing changes implemented in Leopard Server. Apple customers can now run Mac OS X Server, Windows, Linux and other x86 operating systems simultaneously on Apple hardware so we are excited about the possibilities this change presents."
Virtualization is not only hot on the Mac platform for running Windows and Linux, it is also blowing up in the Enterprise. In fact, many enterprise software vendors are turning out their products as virtual machine images instead of software that runs on an operating system. This way the vendor has more control of the operating environment and has less to worry about in terms of incompatibility with hardware or other installed applications on the machine.
Rogue copies of OSX tiger have been running on VMWare for awhile but because most of the drivers are unsupported and not optimized, it is a dog on performance. An Apple blessed and supported version of this would allow a huge leap forward in speed ad performance. It would also mark a big change of direction for the company who has always had a zero tollerance policy for Virtualizing OSX.
And of course, the next logical step – Apple sanctioned Leopard Virtual Machines able to run on any Intel hardware. Will we see Leopard Client running on PCs anytime soon? The next step in that evolution has just been taken.