The XFree86 project (http://www.xfree86.org) is an open source implementation of The X Window System—a.k.a., X Windows, or just X11 (X eleven)—which for many years has brought GUIs to all types of Unix. Less than a year after Apple’s initial release of Mac OS X, the XFree86 team announced stable Darwin support.
The most significant thing X Windows can offer your Mac is the ability to run lots of Unix programs that require a GUI but are programmed using X11’s own widget-working APIs, not Aqua’s. Apple does not bundle X11 support with Mac OS X, however; you have to obtain it separately and install it yourself.
The XFree86 site contains instructions for downloading and installing the X11R6 binaries on a Mac OS X system. The site also provides instructions for compiling the X11R6 suite from source. The easiest way to get X11 for Mac OS X is through either XDarwin or GNU/Darwin, both of which contain easy-to-install binary distributions of X11. Alternatively, the Fink Project includes packages for the X11 server, software, and binaries. Fink also includes the system xfree86 package, which is a placeholder package that lets you use the X11 distribution of your choice with Fink (the placeholder package satisfies the same dependencies as the Fink X11 package).
If you want to install the XFree86 distribution manually, download the XFree86 distribution (see the instructions on ...