I'm going to keep this simple and basic.
I only store user details for login purposes - It usually consists of your google ID or Facebook ID and email address if you have provided one.
The most recent Wavemaker App does not store any of your novel information on our servers - it's all under your control. Whether it's stored locally using one of the standalone apps (ChromeOS or Windows) or in your personal Google Drive account.
The older CARDS app which I am planning on closing down in the near future does store your novel information. However you can download that and export it. I will be deleting the app soon but will send an email to active users with a warning in advance. This will delete all copies of that data..... forever.
Please Note : the current app stores NO data online and the rights and ownership of anything you create using our app is YOURS.