XGGI-on-X ... nothing?

[Brian @ Brightblade]

> XGGI is a complete X-server, you cannot run like Xnest.  You
> can run it alongside Exceed.  The code of XGGI was slightly modified for
> Win32/Cygwin.  It also uses different libraries on Win32 then on UNIX.
John
> Fortin may shed some light on it. Can you not use Xnest from XFree86?
>
> Suhaib

*Newbie alert*
I've been to the XGGI webpage and XGGILib webpage trying to understand what
XGGI is.
Is there a short paragraph somewhere saying why one would want to use XGGI
over Xfree86.

Thanks.