Modifications
 

Is it possible to build a website that interfaces directly with vBulletin forums/threads? In other words, can I build where vBulletin is masked/hidden in the background and a:

1. user has to log in to see any forum.
2. once logged in, user will have the option of subscribing to forums,
3. users subscribed to forums can post threads only in that forum
4. posted threads will only be visible to users subscribed to that particular forum
5. users will get notified of posted threads.

If possible, who can help with the necessary paid modifications?

thanks!

1.yes
2.yes
3.yes
4.by default u can set users up to only see their own threads, to do what you want here would take a little work but not much
5.yes via subscriptions

this is the section you'll want for paid work
https://vborg.vbsupport.ru/forumdisplay.php?f=30

Thanks!