The problem is that a lot of people will google mermaid chart, or come across an extension like this, and find a site that looks like the official website and docs but isn't; it's a paid product with no relation that's simply profiting off of the name. That's deceptive, regardless of whether it's "fair use" or not.
Honestly, I'm surprised anyone on HN would defend that sort of behavior.
Honestly, I'm surprised anyone on HN would defend that sort of behavior.