I don't know what VMware's software does or doesn't do but its documentation just reiterates what OS X's EULA says. VirtualBox's documentation does the same thing [1] and goes further to caution "These license restrictions are also enforced on a technical level. Mac OS X verifies whether it is running on Apple hardware, and most DVDs that that come with Apple hardware even check for an exact model. These restrictions are not circumvented by VirtualBox and continue to apply."

BTW, if you're going to count on Oracle (who owns VirtualBox) for supporting software freedom, you're going to have a bad time.

[1] https://www.virtualbox.org/manual/ch03.html#intro-macosxgues...