I'm in the middle of finishing porting a software-based openGL solution to the xbox (Mesa) and will be done shortly. To use that you can use the OpenXDK which is completely legal (unlike using the XDK) and can release the XBEs afterwards.
Since the XBox has from the ground up been developed only to run one executable at a time there was never any issue of mutually sharing resources (ie, 3d drivers) between processes, so the way that the direct 3d code works is when you compile and link the XBE it statically includes the entire d3d library with the XBE each time.