Currently, the TOTWL is open 7 days a week beginning at 5pm. Access is controlled at a check-in desk on the first floor of the BLT lobby. They pipe in the music from which ever fireworks show is going on at the Magic Kingdom.
Fireworks are at 9:30 on party nights. I also just wanted to mention that you can't go there if you are not a member staying on your membership (so points or cash booked through Member Services) since it wasn't mentioned above.
Policy is you and anyone staying in your room with you. Doesn't hurt to ask at the TOTWL check-in desk. Reports are there are very few people using it.