"No secret alliances. You must announce any alliance in the game chat."
My friends and I have been playing for a while. We interpret it as having to announce the alliance, and that's it. As long as the alliance is known to everybody (via the game chat), then it's fair game. We do not feel the need to disclose any information or deals the parties have agreed upon.
The latest "debate" has been in the game Battle Royale 2 (search for it in another forum

What are your thoughts?