This extends to behavior such as deliberately misleading, or outright lying, to other players in the game. There are no rules against it, so it is completely up to you to decide how honest you wish to be to your allies. Similarly, it is incumbent on you to decide how much to trust the information you have received in turn from your allies.
There is also no particular rule forbidding communication outside of the game (except for no-communication games). If you find it more convenient to use the telephone, or to make your plans head-to-head over a burger and fries, go to it. On the other hand, if you prefer to remain anonymous and keep all your communications within the in-game channels, that's fine too.
No-communication games are different. If you sign up to play a no-communication game, you should be prepared to play it from beginning to end with no attempt to communicate with the other players in the game. No communication means just what it says--no attempt to identify the other players you meet, no attempt to coordinate plans, not even an agreement of mutual non-aggression (beyond what you can achieve through gifting and other in-game tokens of friendship). The reason no-communication games exist is to create a game of pure tactics and strategy, absent the complexity that negotiation and alliances add to the game. If you don't want to play a game without coordinating with your allies, then don't sign up for a no-communication game.
We do also require you to keep all deceit strictly within the context of the game. We specifically forbid attempts to deceive or attack the game server itself. Attempting to hack into the server, or into someone's personal email, to obtain another player's game report or some other in-game advantage is not only wrong, but also illegal. Sending fraudulent email is another example of an ethically and legally questionable act.
We also object to creating more than one RSW account for yourself. There is no reason for any person to have more than one RSW account, other than to sign up both accounts for the same game, which is cheating--it gives you an unfair advantage over the other players in the game. Because RSW accounts are free and can be created without restriction, it's impossible for us to enforce this rule and prevent people from creating multiple accounts, so instead we must appeal to people's innate sense of honesty and fair play. If you want to play multiple positions in the same game, you should sign up for a multi-position game, which gives all players the same advantages. But a single-position game is meant to be played by one player per position, and we urge you to resist the temptation to try to cheat that rule.