This is a small project which releases binary packages for Windows built from the VirtualBox OSE source code releases available on virtualbox.org. Because the name VirtualBox is a trademark of Sun Microsystems, packages made available by this project are named VBox.
The official binaries available on virtualbox.org contain several features not available in the open source version, but are released under a non-free, but still very liberal license. I expect that the vast majority of users will wish to use those instead. But if you only want to use the totally free, GPL licensed version, then normally you would have to build the software yourself from source, which can take considerable time and effort, this should make that choice easy for you.