Version that doesn’t use DirectX has been uploaded for both the demo and the full game. It should not give any problems.
Off the top of my head, yes, all of them do make use of DirectX in one way or another. I suspect the problems here arise not from the usage of DirectX, since it’s pretty much standard in Windows, but from the specific implementation of it used in this particular engine. Then again, having no way of replicating the problem means this is just pure speculation on my part.