I\'m writing a CLI for a music-media-platform. One of the features is going to be that you can directly play YouTube videos from the CLI. I don\'t really have an idea of how
It appears that KeepVid is simply a JavaScript bookmarklet that links you to a KeepVid download page where you can then download the YouTube video in any one of a variety of formats. So, unless you want to figure out how to stream the file that it links you to, it's not easily doable. You'd have to scrape the page returned and figure out which URL you wanted to download, and then you'd have to stream from that URL (and some of the formats may or may not be streamable anyway).
And as an aside, even though they don't have a terms of service specified, I'd imagine that since they appear to be mostly advertisement-supported that abusing their functionality by going around their advertisement-supported webpage would be ethically questionable.