Not. A. Scam. It's legitimate. – Kiwi - Colorful, Custom Keyboard Designer with Emoji for iOS 8 Review

Please... It's not a scam because Apple is just warning you that a MALICIOUS application could steal your information. If you think the people who work here are going to steal your information, you're a snob for not trusting them. Give it a try. It's never happened, and it never will. It does full access because the keyboard runs off the app and can't be accessed unless the app is available and can be 'Fully Accessed'.
Review by Storm Reviews on Kiwi - Colorful, Custom Keyboard Designer with Emoji for iOS 8.