I gave it a try and it works quite nice. Since I am currently using Context/MKII (Installed via the TexLive 2008 distribution) for my documents, your solution would provide even me with a fairly simple method to use the current minimals installation and to try out MKIV. Even switching between "Context-2009-06-11-beta", "gwTeX" and "TeXLive-2008" by using the TeX Distribution system preference panel works. A Testdocument works with "TeXLive-2008" (texexec produktvorschlag.tex) as well as with your installation "Context-2009-06-11-beta" (context produktvorschlag.tex)
:-)
Would it be possible to install (optionally perhaps) third party modules like t-letter and t-simplefonts also?
Yeah, that should be doable. The Apple installer definitely supports packages with several (optional) components. And I think it's a very nice thing to have right out of the box. I'll put it on the roadmap. In the meantime you may install any third party material manually (see below).
Or can I install these third party modules by myself in your "Context-2009-06-11-beta" tree (downloading first-setup.sh in your folder "/usr/local/context/2009-06-11-beta" failed for me, perhaps due to missing rights?)?
Well, you can. If you want these modules to be available to all local users of your Mac place the entire directory hierarchy of each module in the tree /usr/local/context/2009-06-11-beta/texmf-local. You'll need admin access though since /usr/local/context is a protected system directory. If you want the modules to be available only to yourself put their files in ~/Library/texmf (where ~ denotes your home directory). For this you don't need admin rights. Be warned though that the ~/Library/ texmf tree is shared with TeXLive. Hence anything you put there supersedes older versions of the same stuff contained in TeXLive and this might cause some funny interferences when you run an old ConTeXt from the TeXLive distribution ... In both cases you need to issue luatools --generate before ConTeXt recognizes the new additions. If you installed the modules in the system location you need to repeat this step for each local user. Note that this package is still experimental so ~/Library/texmf (as well as most other things) might be subject to change. Oliver