The unxwb project, written by Luigi Auriemma, was released in 2006 under the
GNU General Public License, version 2.0:

http://www.gnu.org/licenses/gpl-2.0.html

While the unxwb project was released under the GPL, Luigi has given express
permission to the MonoGame project to use code from unxwb under the MonoGame
project license. See LICENSE for details.

The unxwb website can be found here:

http://aluigi.altervista.org/papers.htm#xbox