QuickAuth is an open-source user system which supports OAuth. By using QuickAuth, you can log in to some websites without sign up for another account, which most likely will be used only once. Frankly speaking, only my websites would use this system.(hahah)
You don't have to own a Google account, but when you access some Google products, you need one, right?
In short,information such as username, email, verified or not, and some personal information(granted by the user) can be accessed.
This is an implemention of OAuth, and it is proved safe, look at Doc to learn more.