Hans, et al
I'm one of the core Objective-J / Cappuccino developers. I'm glad you like it, and thanks for helping out.
We actually use $OBJJ_HOME in the Objective-J tools already. If you install the Tools package it currently puts all the tools and libraries in /usr/local/share/objj. This is the default used in case $OBJJ_HOME isn't set. If you install the tools elsewhere, you can set your $OBJJ_HOME to that location. We just didn't want to have to set too many environment variables ($STEAM_BUILD is already required, it's where frameworks, etc are built)
Anyway, I like the idea. We probably will be putting a copy of Frameworks at $OBJJ_HOME/Frameworks and the template applications somewhere in $OBJJ_HOME.
We're actually planning on adding some commands for generating standard projects to the "steam" tool (an Objective-J specific build tool, similar to xcodebuild). This would be similar to the "rails" command with Ruby on Rails. Then the TM commands you're talking about would simply call steam with whatever the syntax for a new app is.
Any thoughts?
Also, feel free to join us in #cappuccino on irc.freenode.net
-Tom