Moving to git-based web apps updates.
Please reference the upstream application's updates RSS feed (or another way to watch for updates) in the AppsUpdateFeeds.txt file.
As most web apps are not packaged for debian, it's better to fetch them from git.
Let's create submodules for each app in the wwwroot/ directory.
Keep an up-to-date clone of the nodezero repository on the nodezero machine - by doing periodic git pulls - and when the user wants to upgrade his web app, simply rsync it from their local repo. (Be careful about not overwriting config files thoug, most web apps have theire config in a *-sample config file but some projects may overwrite the user's config). Make sure it doesn't happen during rsync. At first install, copy the app's initial config from a separate initialconfig/ subdir.

Read bout submodules here http://git-scm.com/book/en/Git-Tools-Submodules