Restrictions on creating a virtual machine running Mac OS X Server.
Environment
VMware Fusion 3.x
VMware vSphere ESXi 5.0
VMware Fusion 5.x
VMware Fusion 2.x
VMware Fusion 6.x
VMware vSphere ESXi 5.1
VMware Fusion 1.x
VMware Fusion 4.x
VMware Fusion 7.x
VMware Fusion Pro 10.x
VMware Fusion 10.x
VMware Fusion 8.x
VMware Fusion Pro 8.x
Resolution
You can create a Mac OS X Server virtual machine, with these restrictions:
Due to Apple licensing restrictions, you may only create and run this virtual machine on Apple-labeled hardware. For more information, see Apple's Hardware & Software Product Agreements.
You cannot create a Mac OS X Client virtual machine for OS X 10.6 and earlier. Apple does not allow these Client OSes to be virtualized. With Mac OS X 10.7 (Lion) onwards, Apple has changed their licensing agreement in regards to virtualization.
You can only create a virtual machine using a retail Mac OS X Server disk or image. Virtual machine creation fails when using a disk that came with an Xserve or a Mac Mini Server. Those disks are hardware-specific, and can only be used to install the OS on the physical hardware with which they were shipped. They cannot be used on virtualized hardware.