The article mentions this:

"In January 2006, concerns grew about contributors having access to leaked Windows source code and possibly using this leaked source code in their contributions. In response, Steven Edwards strengthened the project’s intellectual property policy and the project made the difficult decision to audit the existing source code and temporarily freeze contributions."

The allegations have been taken seriously and since then the procedure for accepting contributions include measures to prevent such further events from occurring. If you or anyone else happen to have any plausible suspicion, then please report it to the ReactOS team, otherwise keeping alive this kind of vague and uncertain connection between some Windows code leakage and ReactOS fits the very definition of FUD: https://en.wikipedia.org/wiki/Fear,_uncertainty,_and_doubt Please stop.