From nfo:

For the first time ever, we have made it possible to boot a completely new rom from the hard drive, when booting from ANY kernel. Microsoft provided the ability for debug bioses to be booted from the hard drive or cdrom, but we do not require you to be running a debug bios to utilize this feature.

The advantage of this method over others recently released (by ourselves and others), is that this application will work on ALL bios versions. Previously, the most compatible version was Complex's (great job with the loader plugin architecture guys), but it did not work on the new 5010 and 5101 retail bios revisions. Even though more compatibility is added with each version they still will not work on any new bios revisions to come, without a new release being required for each one. Additionally you are now able to take advantage of newer features being provided by kernel hackers which are outside the scope of simple runtime patching.

We included the full source for the executable. Unlike many release groups, we believe that it is important to share the results of our research with the entire community to foster the rapid development of new features, and to increase the collective knowledge base. This application is based off the xbeboot source code from the xbox-linux team, and does not include any M$ copyrighted code. Please note that the xbox-linux team was not involved with this application, and does not endorse it. Please also note that as this application is a dervitave work of xbeboot, which is under the GNU GPL, this application is also licensed under the GNU GPL, and comes with no warranty, expressed or implied. If you are planning to use the source of this tool for another project, please read the GPL carefully first.

Usage:
You will need to provide your own bios and RC4 key as those are illegal to distribute without permission from Microsoft.
Currently working bioses: X2 4977 Boot From Media version (uses Debug RC4 key)

Future Plans:
We are working to get other debug bioses working with the bootloader. It is likely to be something we can accomplish quickly.

Additionally we are considering trying to load retail bioses as well, however this is a much more difficult task, and maybe more trouble than it's worth really.

Full nfo: http://www.maxconsole.com

Update from http://www.maxconsole:

you can get the debug key from the retail 2bl, so it's pretty easily available to anyone who can get their hands on a retail bios (which is everybody). the bios size MUST be 1024k!

More info about this on #ms-legal EFnet (IRC).

Official Site: n/a, by 'The Phoenix Project'
Download: here (100% legal - no XDK)
News-Source: http://www.maxconsole.com, http://www.xbins.org