Pff. Can't happen to me :-)
Of course I ask myself who spends money in advance for a thing like a proprietary game engine, with all those ready engines, frameworks, APIs and what not around. There's a plethora of examples, some really good (hello Godot), in the open source repositories. I even have the feeling that open source engines like lumberyard/cryengine/amazon_open3d have difficulties getting a foot on the ground because of the let's call it saturation. Not sure what they did so special that others have not accomplished before, but when what Kojack says is true then, then others where at least unsure of that also ...
Let's focus forces on the engine before us, or not ? 😎
Btw., and following my usual agenda, but isn't that an invitation to be ripped off when people submit to an EULA, any EULA ?