If you study the rules of Brainking you can see that there are no prohibitions to use any helps.
Neither books,nor databases,nor computerprograms. So like you say we play a kind of correspondence chess here and the International Correspondence Chess (ICCF) rules also have no prohibitions (alike the rules of our German national federation - Bdf).
So it is not cheating to use any kind of helps.

The simple problem is if you make prohibitions you must have a real control! And this control ist not possible in correspondence chess until now. That`s why it is better to have no prohibitions, otherwise you make the most players to cheaters and this cannot make sense.

For people who are against all kind of helps they can play "Livechess" (face to face) at www.playchess.com,www.icc.com, www.chessgate.de (the last is for free),where all kind of helps are completely forbidden.