This is a bit of a murky area.
Officially, the PDFs from GW are still the current version of BFG.
The FAQ2010 document, which was produced by the high admiralty, is also technically official as the high admiralty was asked to look after the BFG rules by GW. However, when the FAQ was produced GW didn't want anything to do with it (it's not badly written or anything like that, GW just aren't interested in doing anything for specialist games any more).
Anything else is fan-made. By all means use them, but get your opponents permission first.
BFG:Reloaded is a project which hopes to fully update all the rules, FAQ, and fleet lists and bring them together in one book (or series of books) but its not quite finished yet.