So the open source community has a very clearly defined definition of “open” - open does not mean that you can just read the source code. Just reading helps with some trustworthiness, but in order to be afforded all of the protections and benefits of the word “open”, they require some form of ability to fork the code, and to be able to do useful things with that fork. No fork = not open. There are a ton of good reasons for this that I won’t dig into here but you can certainly find by looking up the free software foundation or the open source initiative.
Futo is considered “source available”
There’s nothing wrong per se with what FUTO is doing. They have the right to determine how people can use their code. What is wrong is trying to use the term “open source” which has a very clear meaning to try and win marketing brownie points among its user base when it does not actually follow that definition. It is misleading at best.
Basically: don’t misuse the open source moniker for source-available projects.