MacRumors has discovered that OS X Lion (which will be released sometime in July) allows users to run multiple virtual machines from within OS X using a single license. Previously, only OS X Server allowed the system to be virtualized, and required additional licences for each VM. OS X can only be virtualized on Apple hardware and software, and requires a virtualization program such as VirtualBox, VMware, or Parallels.
(iii) to install, use and run up to two (2) additional copies or instances of the Apple Software within virtual operating system environments on each Mac Computer you own or control that is already running the Apple Software.
This change is extremely helpful for developers and enterprise users, who need to sandbox copies of operating systems for testing purposes. The Golden Master build of OS X 10.7 with the revised EULA was released earlier today.