It looks like the committer made their changes in the top commit, then merged the updated CompViz StableDiffusion change set on top of it for some reason. That's where the license change, rick astley image, etc come from.
And yes, StableDiffusion from the original repo will rick roll you if you try to generate something that triggers its NSFW filter.
Here's the code that does it:
https://github.com/CompVis/stable-diffusion/blob/main/script...
And here's what it looks like: