Because none of the Projects here are written in native mac code, Apple gives you some kind of translation & alternate Window system that is required for something we do here with our Ports.
About X11 for Mac OS X
An implementation of the X Window System that makes it possible to run X11-based applications in Mac OS X. Based on the open source X.org project ÃƒÂ¢Ã¢â€šÂ¬Ã¢â‚¬Â the most common implementation of X11 (10.4's was based on XFree86) ÃƒÂ¢Ã¢â€šÂ¬Ã¢â‚¬Â X11 for Mac OS X is compatible, fast, and fully integrated with Mac OS X. It includes the full X11R6.6 technology including an X11 window server, Quartz window manager, libraries, and basic utilities such as xterm.
Apple's X11 is installed by default on macs, but if you've reinstalled your System or upgraded from Leopard to Snow Leopard for example, it's likely that you didn't install X11.
Because the X11 option is buried in the optional installs tab during the mac OS installation, a lot of people don't select it during install.
Of course, if you don't like to mess around with code from other Platforms (Linux & Windows) like we do, you'd never need X11 anyways.
Here are Mirrors for X11 if you haven't got the Mac OS Install DVD around:
The CXZ Engines (CXZ Ports only)
The CXZ Engines are only required for CXZ Ports and for nothing else.
(What is CXZ and why is it different from other Wrappers?)
Most Wineskin Ports have the Engine built in, but some haven't. The Topic of the Port should clarify this.
For those who are looking for the Wineskin Engines, they are located on doh123's Wineskin Homepage:
Wineskin Engine Downloads
So again as a Summary:
CXZ and X11 required
nothing, you're good to go (RC5, 6 or 7, or 1.0+ based, if its older you need X11 installed)
nothing, you're good to go
always the latest Mac OS update required (10.5.8 or 10.6.3), because some Cider Wrappers aren't working with older System versions.
CX Ports: (*discontinued)
*discontinued because CX Ports aren't working with Snow Leopard anymore.
nothing, you're good to go.