Is it possible to create a channel that calls a website with BrightScript and plays a video from there? The WebView has to accept the input from the remote control.

If no, is there any possibility to develop the whole thing with a web language?

You're in the wrong sub-forum of this board. This is the 'Direct Publisher' channel builder section, which is more along the lines of a Wordpress style template builder. Try posting in the other section.

My 'guess' based on my attempts of using the SDK builder and limited programming knowledge, would be no & no, but others there may be able to give you more definitive & descriptive responses.