Nice job on the active posts.
I take it that when you say it uses a template, you're not referring to a vBulletin template?
I've spent a lot of time with this hack on the UBB trying to find a version that is low overhead. The best way to implement this hack is to hack the posting script so that every time a post is made, an entry is made to either a flat file or a database entry. That way, when the script is called, it only has to make one call/include one file. Also, unlike cron, it is always perfectly up to date.