If you have any more questions, please raise an issue regarding the same on GitHub and I'll answer as honest and quickly as possible :)
Your name and your email address is stored along with your user information, if you signed in with Google, and of course, all the information you input in your resume is also stored in the database. You won't even get any marketing emails, feature updates, newsletters, notification emails, nothing.
Not having a centralized database cause a lot more problems than I could solve, mainly having a large chunk of the users of the app having an outdated schema as the app evolved. This was a problem I could not solve without having at least some control.
Also, a lot of users were having trouble printing their resumes on their browsers, so with the help of Cloud Functions from Firebase, you can now print your resumes remotely. None of the resumes are stored, and they are sent to you immediately after generation, which can be verified by looking through the source code.
Absolutely no catch to this freebie. This project is just my way of giving back to the community that I've learned so much from. If you'd like to show your appreciation however, you can follow me on my social media and let me know how much it helped you, or donate to help pay the cloud bills, or if you are a fellow developer, you can head to GitHub and contribute to the code and raising a PR.
Not yet. But soon, maybe? One of the main motivations for me to shift to a centralized database approach was that I could one day build a mobile app as well that could let users jump from editing on their desktops to editing on their phones. It requires a lot of time, so I would not expect it any time soon, but it's definitely in the pipeline.