This is the vdfuse project ("vdfuse")
This project was registered on SourceForge.net on May 29, 2014, and is described by the project team as follows:
An addon to ubuntu/debian kernel that enables booting a VHD.
Install ubuntu in a virtual hard disk using VirtualBox. Download the vdfuseboot.zip package and unzip into the VM. Set execute permissions to vdprepare.sh and run it as sudo user. This prepares the virtual hard disk to be bootable from grub.
Use vboot grub bootloader provided to install a grub entry for windows. Edit the grub.cfg file of the grub bootloader to include an entry for the ubuntu virtual hard disk based on your setup. Some examples below,
menuentry "Ubuntu-Regular-Install" {This should get you up and running.
Of benefit to users, Open Source software is licensed so you can download and use the software free-of-charge. The source code for this software is made available free-of-charge, you (or a programmer you hire) can make changes to this software to better meet your needs, and you can release your changed code back to the community passing the benefit on to other users.
The exact license terms used by this project on their project summary page and in the licensing documents included in their downloads.