Twitter like all of the "social networks" change their API often. If the Twitter modification was not updated this year on vBulletin.org, then of course it will be using the old API. If your not looking for anything fancy you can simply add the twitter feed widget from "Twitter" and insert it into a forum block (sidebar) or cms widget. Most of the API systems change either due to user abuse of the "social networks" resources, or for the "social network" to promote/force limited push advertising to your page.
You will need to pass the Twitter feed widget an ID of the feed you are following. If I understood exactly what you were looking for I could be more helpful.
Since there is very little you can modify to receive a feed from Twitter, there really is not a reason to create a vBulletin modification. Although caching, would definitely help if their feed's are rate limited under your defined use.
https://support.twitter.com/articles...-and-following
https://support.twitter.com/articles/160385