X11 in Mountain Lion
A couple of people have contacted me about the news that X11will not part of the standard distribution of the next version of the Mac operating system. X11 is a key UNIX windowing system for a number scientific applications and I can understand the concern. However whilst X11 has been included in the past it should be noted that the distributed version is simply a snapshot of XQuartz, in the future this will be automatically downloaded.
The XQuartz project is an open-source effort to develop a version of the X.org X Window System that runs on Mac OS X. Together with supporting libraries and applications, it forms the X11.app that Apple has shipped with OS X since version 10.5. It may in fact be better if users download the latest version of XQuartz when needed since they provide regular updates which are unfortunately overwritten when you install a Mac OS update.
Indeed the team have already provided a latest development version that is compatible with Mountain Lion (XQuartz 2.7.1 rc4 - 2012.02.11), if you find any bugs or issues I urge you to report them to the XQuartz team !