Owner key is not required and I don't think it will ever be..that's why it is a disabled textbox in the images. It will be removed before the app is released. Secondly, I agree about security and I am adding the option for users to encrypt the key with a password when the app is first used..but they will have to enter the pass everytime they open the app because that will not be stored. That's the best I'll be able to do for assurances.
RE: Introducing Steem Exchanger, A Desktop App To Manage Your STEEM Account and For AutoTrading Tokens at Steem-Engine.com