Probably all other dlls that we forked or always developed on our own (except ntdll, gdi32, user32, kernel32) could be developed against Windows. And what about drivers, services, cpls, shell extensions, explorer, cmd, user mode apps, ...
That was the biggest mistake of ReactOS project from the beginning! Instead of developing against Windows, people developed against [broken] ReactOS. Wasted time.
WBR, Aleksey Bragin.