I don't know what the downvote is for, from the SLA [1]:

    (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, for purposes of: (a) software development; (b) testing during
    software development; (c) using OS X Server; or (d) personal, non-commercial use.

[1] http://images.apple.com/legal/sla/docs/OSX1010.pdf