Sun Microsystems does not provide binaries for their open source edition (OSE) of Virtualbox. The name, OSEbox is of course short for Open Source Edition Virtualbox.
The binary downloads available at the Sun site is only for personal use and evaluation.
As Virtualbox OSE is released under The GNU General Public License (GPL) Version 2 license, we aim at providing you with instructions for how to build the open source edition from the source available and at providing the binaries themselves.
Please feel free to contribute with enhancements and builds so we perhaps can provide some of the features missing in the OSE version.
We are starting out with OSE.x86 for Windows.