Yes, this engine can be used to make commercial games. Simply put me in the credits (and not resell it). Please be aware that this a working in progress project, that will grow over time. It is not finished now but if what you see is enough for you, well you can use it any way you like.
There is not demo, only the videos on my youtube channel that shows what you can aleady do/what you get. https://www.youtube.com/channel/UCeG_QgoqaE---bsr9h0VQxg