Mac OS X uses Darwin.
I'm not sure if you mean the foundation of Mac OS X itself, or of the desktop. The desktop is a part of Mac OS X's Finder application which is written by Apple from scratch in Objective-C using the Cocoa framework. Mac OS X itself's core is Darwin, a UNIX operating system based on the open source FreeBSD.
The Darwin kernel of Mac OS X is open source, as are many other parts of the OS. (See links below) but Mac OS X itself is not open source and Apple only allows it to run on Apple hardware.
The second name of Mac OS X v10.4.5 is Mac OS X v10.4 Intel.Mac OS X 10.4 was known as Mac OS X Tiger.
Mac OS X 10.4 (Tiger) needs to be purchased as it is not possible to update from Mac OS X 10.2.8
Mac OS X is an operating system released by Apple Inc. It is designed for Apple branded computers, which is why you will never see a Dell, or an HP computer run Mac OS X. There are only two important versions of Mac OS X, Mac OS X Server, and regular Mac OS X. Mac OS X server was designed for servers, while regular Mac OS X was designed for most computers. The current version of Mac OS X (10.6) is named Snow Leopard.
Yes, it is. Any type of MacBook that comes out now is a Mac OS X. The most recent version of Mac OS X is Mac OS X Lion, coming out soon.
Mac OS X is based on UNIX.
The 4 Applications that were released were: 1. iTunes 2. iMovie 3. iPhoto 4. iDVD All of these were created to run on OS 9 until OSX came out. All Mac OSX Releases (in order): -Mac OS X Server 1.0 "Hera" -Mac OS X Public Beta "Kodiak" -Mac OS X 10.0 "Cheetah" -Mac OS X 10.1 "Puma" -Mac OS X 10.2 "Jaguar" -Mac OS X 10.3 "Panther" -Mac OS X 10.4 "Tiger" -Mac OS X 10.5 "Leopard" -Mac OS X 10.6 "Snow Leopard" -Mac OS X 10.7 "Cougar" (still in development, scheduled for 2011 release)
It runs a pared down version of Mac OS X with a FreeBSD sub-system. It also operates over a Darwin Kernel for those who are interested.
Mac OS X can only be installed on Apple hardware so Vmware is unable to support Mac OS X on anything other than a Mac by running, for example, a virtual installation of Mac OS X Server on a standard Mac OS X machine. Conversely Vmware's Fusion allows the running of Windows, and other operating systems, on an Intel Mac running Mac OS X.
You cannot without erasing your hard drive and installing Mac OS 9 from scratch. Even then Mac OS 9 may not run on modern Mac hardware because Mac OS 9 needs the ROM chip to boot. Modern Mac OS X hardware uses EFI to boot the system instead of a ROM chip to boot. Mac OS X v10.0 - Mac OS X v10.4 support Mac OS 9 applications and can run them, you just need to install the Mac OS 9 compatibility program which can be found on the Mac OS X Install CD.