What is a Touchcast? In the words of the founders it is not broadcast which quickly becomes clear. A touchcast means that all kinds of web content can be incorporated into a video such that viewers will be able to interact with that video in ways they never imagined. Video apps or "vapps" as they are called become the basis of being able to interact with the live web on replay. Think of a video, in effect, becoming the browser such that a 5 minute video can become the basis of 15 or 20 minutes of browsing depending on which vapps are employed within it. If nothing else the teaching applications that Touchcast will be able to support will be amazing.
The key is that the original Touchcast app for the iPad effectively allowed a tablet to replace many of the features of a very expensive video production studio including uses of video footage as a background, a green screen effect a sophisticated teleprompter and a lot more. However, the new PC desktop / laptop version announced at the NY Tech Meetup goes further allowing different cameras to be selected on the fly including adding interactive elements such as polls, social media accounts, Google Maps, to videos.
Take a look. My gut says In the long run YouTube may just want Touchcast or all of the Touchcast features for themselves especially now that Touchcast includes a vapp for Youtube which will help sell it to Youtube.