BU is not a party school like traditional party schools. That being said, it doesn't mean that no one ever goes to parties or drinks. But we're in the city of boston, we won't have the same dynamics as schools in the middle of no where with nothing else to do.
The guest policy is just that if you want to bring someone into your dorm that doesn't live on campus as BU, you have to sign then in and they leave and ID with the guard. Very painless.
As far as adults being strict on drinking, just don't be dumb and loud about it or throw a house party with 200 people.