X11.app was initially available as a downloadable public
beta for
Mac OS X 10.2 Jaguar and later included as a standard package for
Mac OS X 10.3 Panther. In
Mac OS X 10.4 Tiger X11.app was an optional install included on the install DVD.
Mac OS X 10.5 Leopard,
Mac OS X 10.6 Snow Leopard, and
Mac OS X 10.7 Lion installed X11.app by default, but from
OS X 10.8 Mountain Lion on Apple dropped dedicated support for X11.app, with users being directed to the
open source XQuartz project (to which Apple contributes) instead. In
Mac OS X 10.4 Tiger, Apple's X11 implemented
X11 protocol release 6.6 (X11R6.6). This implementation includes an XFree86 4.4 based X11 window server,
Quartz rootless window manager, libraries, and basic utilities such as
xterm. "Rootless" means that X window applications show up on the Quartz desktop, appearing like any other windowed Quartz application (that is, not in a virtual desktop contained within another window). In
Mac OS X Leopard, X11 was updated to use
X.Org Server (X11R7.2) rather than
XFree86. The source code for X11 is available from Apple. Some source code is available under the
Apple Public Source License while the bulk is licensed under the
MIT License. == Current version ==