[Hellcat]

Yes, this is very much possible and I do that on my own site a lot as well.

You can query the user table of you vB installation for the username and the password and compare it to what ppl entered on your own login form.

The password is stored as a MD5 hash in the database, so you'd have to compare the hash of the entered password to the hash stored in the DB, instead of the actual passwords (security reasons).

What you also could do is to read the (session) cookie vB sets on the peoples local computer at process that in your own PHPs, so once logged in to vB your visitors would automatically be logged in to the rest of your site.

Yet another option would be to actually use the vB backend functions in your own scripts, that saves a lot of work