That's a claim that... at best it seems that hasn't yet gathered behind it enough motivation to clarify anything, and at worst is just a plain malicious FUD. It doesn't even matter, when you think about it. Even if we'd assume a legal accusation of leaked-resembling code in all that pile of modules, all that ReactOS team needs to do is to formally contract reimplementations by independent teams for any of those allegedly guilty modules. In this light, such an accusation is very unlikely to happen, and probably there won't be even a half-baked effort to officially demand clarifying and putting any potential issues to rest. So, about those people out there with an interest in painting ReactOS as plagued by leaked code, entertaining this uncertainty is all they'll do, nothing more.

"You can look up the «history» of it and how it has symbol names for companies with whom Microsoft worked to solve specific application issues."

I assume you aren't going yourself to provide a reference to what you're alluding to in that public repository?