If you do not trademark your name then I can only assume you do not want exclusive control of that name - I certainly wouldn't assume you want the protections a trademark grants.

To me it sounds like when open source project resenting a very-permissive license just after someone else turns it into a profit machine. Kind of sucks but also the whole point of that permissive license is you shouldn't care.

It's not uncommon for companies to piggyback off an open source project's success and mislead people into thinking it's theirs. Seemed an awful lot like that was the case here.

I am Knut Sveidqvist, the inventor of Mermaid and creator of the Mermaid open-source project. I'm also the co-founder of Mermaid Chart.

To address the confusion: Mermaid Chart is not a separate entity "profiting off the name" - it's a commercial offering I created to help sustain the open-source project. Working on Mermaid during evenings and weekends became unsustainable as the project grew. Mermaid Chart allows me to work on what I love full-time while providing resources back to the open-source project. This support will continue to grow as our business matures.

I appreciate your concern about protecting users from deceptive practices. In this case, there is a direct connection between the open-source project and the commercial offering, created by the same founding team.

For diagramming and even UI prototyping I keep getting back to plain old ascii drawings though. Asciiflow.com is fantastic. I just wish they had vim keybindings. It's also great to embed in .md too. Could mermaid generate ascii? It just seems easier to comprehend and doesn't need a separate renderer.

Saying "that's legal; if they didn't want it to happen they'd have trademarked" is the correct response. We can socially shame a behaviour on a random comment section on the internet, or we can actually provide the solution to all future people: trademark it if you want it.