I believe I'm the author of the script he's attempting to modify. It is posted in this thread:
http://forums.omnigroup.com/showthread.php?t=12955 and the code for grabbing the list of stuff to process is essentially identical to the usual construction of your scripts, I think. It relies on the user having already selected something in the sidebar, and that's the part that the OP wants to script.
I don't think there's any Applescript support in OmniFocus for taking a snapshot of a perspective, though you could probably do it with UI scripting.