Apple introduced Native JavaScript bridge for iOS in iOS 7. you can call objective-c apis in javascript.[1]
[1]https://developer.apple.com/library/mac/documentation/AppleA...
[1]https://developer.apple.com/library/mac/documentation/AppleA...
Update: the docs are up and the JS framework is called TVJS, https://developer.apple.com/library/prerelease/tvos/document...
If you're wanting to stream video you can build a full app with almost no Obj-C/Swift (there's still a small shell, though probably nothing custom needs to be here).
The XML templates are a little odd in that they're JS files (e.g. Index.xml.js) and contain the XML as the return value of a global function called Template.
It seems really straight forward though.