I followed all these steps to install MkIV on a Mac and to run it with either Smultron or TexShop :

http://wiki.contextgarden.net/ConTeXt_Minimals/Mac_Installation

However it works fine with Smultron (but I am more used to TexShop to run TeX files), with TexShop I get :

MTXrun | unknown script 'context.lua' or 'mtx-context.lua'

Even after running the following command line :

luatools --generate

it doesn't help at all.

Thanks for any hint,

Mathieu