You can render HTML content with a custom rendering engine - for example ePub ebooks are essentially bundled HTML + CSS content - there are several HTML rendering engines that read ePub ebooks but don't use Webkit.

Also, you can build a UI using web languages and render to native controls, all without using WebKit if you'd like.

Right, rendering HTML is fine. As long as you don't download it from the internet on-demand, or so.