The iOS system is a branch off the original OS, which is not available on your mobile device. Legally and formally speaking, any official documents for any game or application available on the device or app-store is originally located on an official public domain for the company/provider. If it is not listed, then it probably doesn't exist.
That being said, Graal does have a website with the rules for you to read... While having these rules stated within the game itself is unnecessary, if people have a legit problem with its absence, then hell, stick it in there. No reason not to.
Lockdown, it is also possible to access most domains from the iOS. Many have mobile versions of the website, but it is possible to reach the full site from a mobile device. Graal does not have a mobile site (last time I checked), but you can find the site and read the rules from your iDevice if you really wanted to. Also, no iDevice application requires you to accept rules and agreements before downloading. This is not uncommon behavior. Anything inside the app itself is a different story; that's up to the app owner, as long as it fits under Apple's rules as well.