It’s worth mentioning that there’s currently a Kickstarter campaign to open source Sciter https://www.kickstarter.com/projects/c-smile/open-source-sci... it’s by the author who seems to have some worthwhile goals for using the money besides simply opening up the code.
It looks great. I personally have nothing against HTML UIs other than electron's excessive resource usage. My primary complaint is that chrome's engine was never meant to be used once per application. Sciter fixes that.