In general (I’m not saying this is the case with this project) if you don’t have their prompt history and you can’t re-run the LLM “compilation” yourself, is it open source? It feels a bit more like those “source available” projects where you can read the code but don’t have access to the build system.
On the other hand, aside from the commit messages, one didn’t ever have access to the underlying thought process of human developers either, so maybe it’s not equivalent to say that secret prompts mean closed-source.