From the original source 12factor.net (4 points, 6 hours ago) https://news.ycombinator.com/item?id=42128769

What does it mean to open source something that is not source code?

Well, in this specific case there is source code and it's the source to the website, which now accepts contributions rather than just being "read only." The linked article goes into why they are now open to contributions

I am not lawyerly enough to get into whether the Creative Commons are "open source" but shrug https://github.com/twelve-factor/twelve-factor/blob/main/LIC... seems to be pretty liberal with the rights offered to others

Thanks. I wasn't trying to be snarky. I really couldn't find where that was explained in the article. I guess I should have followed the links.