Plagiarism is a moral wrong.
But copyright infringement is a legal wrong (a civil liability).
Is what they're doing infringing on a copyrighted work? Or does it fail to uphold license terms? Many open source licenses have some amount of attribution as a requirement, so that'd be something to consider.
AI is actually beginning to encourage "restricted source", public-only-gets-binary debates to simply avoid such legal issues.
Write a snail-mail letter to get the real sources. Repositories are private with a small well-vetted list of contributors. Also avoid slop-PR headaches that away.
It's addressed in the post. MIT license. Zigbook is not honoring the attribution requirement. A PR to change that was closed and obfuscated.