sorry to bring this back from the dead...

but I was thinking the same thing (of course, I'm new to vBulletin)

When I think of a mod, I'm thinking of a self contained modular addon to vBulletin. Hack makes me think of a hack to the core code of vBulletin. But maybe there's a lot of overlap here... as a vBulletin newbie, it sure feels like it isn't very modular as almost every feature I've added required me to hack the core vbulletin code. As an enterprise forum solution, you would think that it would have a robust enough API so that it would be rare to require added fields to a core vBulletin database table, or changes to the core php files... sure would make upgrading easier.