Reaction

ReactOS started not "in the Vista days" but much earlier. Its earliest iteration was called FreeWin95 and started in 1996, Version 0.0.11 came out in 1998 and version 0.1.0 in 2003.

So it did not start out as a retro project which willy-nilly it has become over time, but as an effort to replicate a current production OS, just as GNU and Linux did with Unix.
- dasGagaTier