The author points out that they just want two-way databinding, and don't want the entire overhead of Angular. Most of the Angular overhead is directives that you probably would use /anyways/, and are actually just written in Angular.
Ostensibly, you could fork Angular, take out all the custom directives, and end up with a much smaller starting codebase.
But then you'd end up re-implementing a lot of the default Angular directives (like ng-loop), and likely have a buggier application for it.
The author points out that they just want two-way databinding, and don't want the entire overhead of Angular. Most of the Angular overhead is directives that you probably would use /anyways/, and are actually just written in Angular.
Ostensibly, you could fork Angular, take out all the custom directives, and end up with a much smaller starting codebase.
But then you'd end up re-implementing a lot of the default Angular directives (like ng-loop), and likely have a buggier application for it.