There's more to this. They won't name the person, and comment wasn't sought from this person. They also don't want a witch hunt. But it sounds like this person is trying to destroy the project from the inside out?
So in general, for those who don't want to read the article, the project is being worked on by several (unknown number of) volunteers. One person joined, and made contributions. That person then left, and demanded the team remove their contributions. The team did so. They are still threatening to sue, which would expose the identities of everyone involved.
Sounds like sabotage to me.
I'd be interested in hearing from this former team member and what they are actually trying to accomplish, though. Because as far as I know, Bethesda is fine with this project as long as they don't use any official assets. And it sounds like they aren't. So, who stands to gain from the project being killed (i.e. if the developers get doxxed)? Steam/Valve, because they sell the PC version of the game? I don't buy it. Sony? That's an even greater stretch.