It isn't open source, it's source available. You have not licensed your source code, it is thus under copyright.
Please read the open source definition; https://opensource.org/osd.
There are other phrases that are usable, such as source first (in the case of FUTO licenses) or source available (when source is under copyright but is provided).
The engine, being actually MIT, is however open source.
Thank you for licensing your project. I appreciate your commitment to open source. More developers and people should be like you.
"open source" is not a trademark. Technically he can say whatever.
I don’t think Katdork is claiming the phrase “open source” is protected. He’s just saying it’s inaccurate in this case. Like claiming a fish has arms — the statement is legal, it’s just wrong.
I'm saying that words have meaning and that meaning should ideally not diluted. But, considering the developer licensed their project as MIT, I'm very happy.
Looks like MIT license has been added to the game now too.
Unfortunately no README.md