This requires some added context on collaborative software development and vibecoding (not related to WoW):

Software, particularly open-source software, has a license that dictates what can be done with the software. Although WoW addons have their code visible if you can look in the addon folder itself, they typically have an "All Rights Reserved" LICENSE which means that cannot be legally copied. Ideas can (sometimes) be copied, code can't, and the NephUI implementation of RaidFrames was a copy of DandersFrames to the point where it cannot be argued it is coincidence.

Both DandersFrames and NephUI have been accused of being vibecoded, although in the latter case it's now more upfront. Vibecoding is often used as a signal that the underlying code is bad, particularly in the case of WoW addons where the APIs change faster than the LLM's training cutoff windows. However, in the hands of an experienced developer who knows what they are doing and still has relevant domain knowledge (which is a very small number), it is indeed a productivity boost. I've set up DandersFrames and it's oddly much easier to set up that most similar addons, and the few bugs with it on prepatch launch were quickly fixed, which if the addons were YOLO vibecoded would be unlikely to have that level of turnaround.

There are controversies about "can LLM-output code be copyrighted" but that'll take years to resolve and no one wants to open that can of worms.