The purpose of Hybrid Core is to have a solid PHP code base for theme developers to build from. It is a modular framework that allows the developer to pick and choose commonly-used features in themes.
If building custom themes on top of a true framework interests you, please read the more-detailed explanation of Hybrid Core.
The Hybrid Core framework is not a WordPress theme. You cannot install it into WordPress and expect it to work. It is a development framework for building custom themes. If you’re looking for a theme that you install, head on over to the themes page.