Yeah, but if you read carefully, section 4.7 explicitly says that you must use WebKit and JSC to run third party software. Therefore, you can use your own engin

Yeah, but if you read carefully, section 4.7 explicitly says that you must use WebKit and JSC to run third party software. Therefore, you can use your own engine to render your app (see games or Google's Flutter), but you cannot use it to render third-party content (thus making impossible to create a browser)