See this: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui... That explains some stuff about the DdEntry and GdiEntry stuff...
Oh well, they added some DDK docs in the MSDN (which were not really there last time I looked)...
But it's as we feared : they explicitely tells us that this interface may change on each DirectX revision (which is normal as the driver interface need to change to accomodate more advanced graphic options). So we may have to rewrite 'old' DirectX code each time a new revision of the DDK comes out.
Anyway, the current code is current not written at all with a DLL / Driver separation in mind (there are some plans about it, but nothing has been done yet from what I know). And you should speak to Raphael about this, he's the one motivated to do this (I am not, as getting more games to run is more fun than to rewrite everything :-) ).
And more people to code would be welcome of course. And I think if you really want us to go the DDK way, you would need to at least do part of the work yourself :-)
Lionel