Users interacting with TeX using a front end program are sometimes unaware of the vast support machinery acting invisibly behind the scene. This machinery consists of Donald Knuth's command line program, which does the actual typesetting, and of an enormous number of fonts, macro packages like LaTeX and ConTeXt, style files, documentation, configuration files, and the like. The enormous collection of programs and support files is called a TeX Distribution.
For a number of years, the standard TeX distribution on Unix machines, Linux, and Mac OS X was teTeX, maintained by Thomas Esser. On the Macintosh, this distribution was enhanced by Gerben Wierda, who wrote a program called i-Installer to download his enhanced version from the network, to configure it, and to upgrade it periodically.
Several years ago the TeX Users Group (TUG) introduced an even more extensive distribution called TeXLive, for Unix machines, Windows, and Mac OS X; the principal authors are Sebastian Rahtz, Karl Berry, and Staszek Wawrykiewicz. The current version of TeXLive is TeXLive-2005, introduced in November, 2005 for the year 2006. The next version of TeXLive, TeXLive-2007, will be introduced in January, 2007. Gerben's distribution used TeXLive as the source of all programs, and used teTeX for style files, fonts, etc.
On May, 2006, Thomas Esser announced that he would no longer support teTeX, and suggested that users move to TeXLive. This caused a scramble throughout the TeX world; in particular Gerben Wierda has worked to move his i-Installer supported configuration to TeXLive. The new configuration is called gwTeX.
In November, 2006, Gerben Wierda announced this new version at the TUG conference in Marrakesh, but he simultaneously announced that he would end active support in January, 2007, although he will continue upgrading the system to meet his own needs. At this date, it is unknown whether others will step up to maintain active support.
This left Mac users in a quandary: should they use the original distribution, upgrade to Gerben's gwTeX in hopes that it will be maintained by others, or bite the bullet and switch to the full TeXLive? Actually, this is only a "theoretical" problem because Gerben's gwTeX is being actively developed at the moment and will remain useful for years even if development stops; after all, TeXLive is only upgraded once a year.
These various distributions differ ''only at the edges;'' the vast majority of programs, style files, fonts, and the like are the same in all distributions. Most users would notice no difference when moving their source files from a system based on one distribution to a system based on another. But the various files tend to be upgraded by their authors, so it is desirable to use a distribution which will remain up-to-date.
The new MacTeX packages allow users to experiment with all three distributions. They are configured so Mac OS X GUI programs see the same interface regardless of the TeX distribution used. Indeed, the user experience with these new install packages is essentially the same as the experience with the original MacTeX.