Darling is written in a different language so I don't think the LLM would copy paste code from it directly. But it is the main (only?) prior art, so it could be argued that everything the LLM knows about how to do this came because it read and understood Darling, i.e. if Darling didn't exist it may still be able to do this but it would have to figure it out from first principles.

Not saying it happened here, but it's an interesting thought experiment: what if you order an LLm to achieve the same goal as a popular open source project, using all the lessons learned and pitfalls faced by that project, but not to copy the code. Indeed, LLM code is now often better than human code, so direct code copying would be a disadvantage. Humans are certainly inspired by other projects like this all the time and it isn't considered plagiarism.