By only using available documentation like
MSDN, books about Windows internals and the source code of
ReactOS I can be (mostly) sure that my code will be free of copyright problems. The last I'd want for the Free Pascal / Lazarus community is a copyright infringement.
x64 is only a small problem. All I'd need for it is a VM with a 64-bit Windows and some small adjustments inside the compiler. But first I want to test everything on a system I can debug and that is ReactOS which is currently only supports 32-bit. And most important: I first need to fully understand how the NT kernel (including driver development) works.
Regards,
Sven