"In fact, with WINE there's no need for Windows at all. WINE
creates an environment that responds to Windows API calls, so apps
'think' they are running in Windows, when in fact there's no
Windows there at all.
"The difference between the two applications is that CrossOver
uses a proprietary, more up-to-date version of Wine along with some
handy extensions. The two also differ as far as support; CrossOver
is commercially supported by CodeWeavers while Wine relies on the
community for support."