I can't even tell if this repository is based on prompts extracted from Claude Design or if the author had an LLM create all of these prompts in it from scratch.

The fact that they encourage and accept PRs indicates that this isn't intended as a direct prompt extraction exposure project - plus the license, which should indicate they have the authorship necessary to license that content.

Assuming this IS a complete ground-up implementation it really needs to link to demonstrations that it works. Without any evidence it's hard to justify spending time exploring it.