Use the documentation of WRK (it is maily Windows Internals 4th edtion + additional chapters, afaik). I think we shouldn't use use their WRK for any other purpose then as a documentation (and only if it is okay with the GPL and the MS Eula/license/etc.).
All other "alternatives" doesn't make sense to me.
"ReactOS is aiming to run your applications and use your hardware, a FOSS operating system for everyone!"
Read more on http://www.reactos.org ;-)