You can get the requested files
here. As you can see they are fairly slim because they use the SSI (Server Side Includes) feature of this forum software to grab content. So if you want to provide your own news/changelog you'd have to return your own content, unless you want to use SMF also.
If I would make this today, I'd have some script that fetched structured data like JSON or something instead and then generated the HTML markup needed instead of simply including raw HTML.
The launcher uses a webview using Internet Explorer (or maybe edge on Windows 10?) so any content could go their really...