There's a new project to replace the XQuartz DDX, as used by Apple Mac OS X, with the stock XFree86 DDX using a dummy video driver.
Jamey Sharp and other faculty at Portland State University are facilitating another X-related capstone project with the focus this time of moving rootless (in terms of no root window, not as running X.Org Server as an unprivileged user) out of the xorg-server. The goal is to replace the functionality offered right now by the X Server's root-less layer and the XQuartz input/rendering. Part of this work entails writing a compositing window manager that can grab window contents out of the server and then blit them into native windows on the host.
While XQuartz is really only relevant on Mac OS X / Darwin, they hope the resulting client code will be of use on other operating systems too. Part of the hope is that it could replace XWin with a Windows version of this compositing window manager. There's also thinking that it may be of use as well to the Wayland Display Server.
This project is still early, but they're hoping to have it completed by next March. Based upon the track record of previous X.Org projects at Portland State University, it will hopefully be another success. More details can be found in this xorg-devel message