1: Nobody "released the Aliens", Rudy. I'm not sure what you meant by that. 2: Whoever sent the Nostromo out, obviously trashed all the data, for fear of criminal involvement. Nobody in the company knew about it. Why? Because they would have sent out another mission in the 57 years between the Nostromo going by Acheron and Ripleys' return, otherwise. Certainly, they wouldn't have bothered to help fix the colony up. They would have simply gone and got eggs. Burke took a risk. It was his doing so, which presumably cued others in the company to search hidden archives. Hence, the team in 'Alien 3'.