First, thank's for the answer.
My question was only a doubt, i don't understood why is private, and that's all, nothing's serious.
However, i appreciate your response and, for the next time if the BB team want consider to create torrent public, it can be a great thing. Hoevere i'll going to upload it on major sites of torrent (like v. 4.5 and 4.3), private or public is not so important

You can close, thank's for your time and
always thank's for your work