"Oni 2 is licensed under the CC-BY-NC-4.0 license."
CC licenses are not a good fit for software in general - and "non commercial" isn't very clear. Making something available at zero cost doesn't necessarily make it "non commercial".
Ed: and it means that code snippets/widgets from oni2 can't be used elsewhere without careful licensing - which is one reason cc/NC is a poor fit even for code examples - it's for education, but you cannot use what you learn...