I realize not everyone loves to read a wall of text. So here’s a synopsis.
SJ is switching engine because I have the feeling that the open source engines are not dependable and their authors not committed enough. My fear is that a nasty bug pops up when the game ships (or during testing), and the engine coder is not motivated to fix it at that time. With a commercial game, this is a pretty bad scenario that could get ugly fast, especially that late in the development process. Consider people writing angry reviews and wanting their money back – this is something that can’t be allowed to happen.
The decision was not rash; there is a two-year history and a collection of issues behind it (even longer if I count the mod project preceding it.) It is not a personal thing, it is a management decision for the best of the project. I realize that such decisions might be viewed as harsh. Consider that they are also harsh on the one who has to make them.
One could make the argument that these engines are free, thus it can’t be expected for them to be fully dependable. From their perspective, that is correct and it is hard to argue with that.
From my perspective it matters little, because what good is any engine that might fail at a critical time? No matter if it is free. Consider that Unity is also free.
I hope this is easier to read.