I've hacked together this code and the DCS headtracking interface, but I haven't got the time to get the compile environment set up. The source is here:
http://www.tjhowse.com/dcs/HeadTrackerDll.zip
No doubt it'll require some jiggery-pokery to get it to compile, but the fundimentals are there. This SHOULD result in a DLL that loads the freetrack DLL and act as a proxy between freetrack and DCS games.
--Scythe--