The XQuartz project is an open-source effort to develop a version of the X.Org X Window System that runs on macOS. Together with supporting libraries and applications, it forms the X11.app that Apple shipped with OS X versions 10.5 through 10.7.
OS X Software Updates have included some of the work done by the XQuartz project, but for various reasons, Apple cannot ship the latest and greatest version offered by the XQuartz site. Since the XQuartz X11 package clobbers Apple's X11.app, their software update will clobber the XQuartz X11 package. Because of this, you may experience conflicts after doing a Software Update from Apple. Please re-install the latest XQuartz X11 release for Leopard after installing a system software update to OS X 10.5.x Leop
An XQuartz installation consists of many individual pieces of software which have various licenses. The X.Org software components’ licenses are discussed on the X.Org Foundation Licenses page . The quartz-wm window manager included with the XQuartz distribution uses the Apple Public Source License Version 2 .
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