I'd still consider them more similar than not.

Hurd was not a research project initially. It was a project to develop an actual, usable kernel for the GNU system, and it was supposed to be a free, copyleft replacement for the Unix kernel. ReactOS was similarly a project to make a usable and useful NT-compatible kernel, also as a free and copyleft replacement.

The key difference is that Hurd was not beholden to a particular architecture, it was free to do most things its own way as long as POSIX compatibility was achieved. ReactOS is more rigid in that it aims for compatibility with the NT implementation, including bugs, quirks and all, instead of a standard.

Both are long irrelevant to their original goals. Hurd because Linux is the dominant free Unix-like kernel (with the BSD kernel a distant second), ReactOS because the kernel it targets became a retrocomputing thing before ReactOS could reach a beta stage. And in the case of ReactOS, the secondary "whole system" goal is also irrelevant now because dozens of modern Linux distributions provide a better desktop experience than Windows 2000. Hell, Haiku is a better desktop experience.

"And in the case of ReactOS, the secondary «whole system» goal is also irrelevant now because dozens of modern Linux distributions provide a better desktop experience than Windows 2000. Hell, Haiku is a better desktop experience."

Yet, there are still too many desktop users that, despite the wishful thinking or blaming, still haven't switched to neither Linux, nor Haiku. No mater how good Haiku or Linux distributions are, their incompatibility with the existing Windows simply disqualifies them as options for those desktop users. I bet we'll see people switching to ReactOS when it will get just stable enough, yet long before it will get as polished as either Haiku or any given quality Linux distribution.