Project died on Jan 6 2008. They could not make it work.
Even if they had they would have been stomping all over MS intellectual property and would have been sued into oblivion. DX10 is the only real added capability in VISTA over XP. The rest is slower code, eye candy and security patches. MS will never allow porting DX10 to XP.
DX10 is not public domain and can not be legally reverse engineered and moded.