Oh you’re assuming the content in this repo is taken from somewhere? There are other sibling threads about this; you might be mis-interpreting the title.
Oh you’re right, sorry! Well unless the Claude Design prompt is open source licensed, then correct, it’s not legal to publish it under an open license. That would be a copyright violation.
Even if you rewrite an article in your own words, you cannot claim copyright for that. At least, not to my knowledge.