From the introduction:
This document is intended as a source of information for players who are including the brotherhood in their campaign, or are playing brotherhood characters.
Much of the information in this document is totally unofficial and original, due to a lack of good official information about the brotherhood, and you may not agree with everything in this document (in which case you are of course free to change it to your hearts content). I do however think that where I have added new material, that it strengthens the atmosphere of the brotherhood, rather than detracting from it.
You will need a copy of the Fallout PnP rulebook by Jason Mical to play.