Sure, you can include a link to a YouTube or Vimio video in an Adobe Digital Publishing Suite app, but often it is much better to embed the video within the app. This way, the user doesn't need an internet connection to play the video.
As I've helped numerous corporate clients create their DPS apps, I've found that oftentimes they don't have access to the original MP4 video footage. All they have is what someone else in the company has posted to YouTube.
The trouble is, you cannot “save” video from YouTube to your local hard drive. But a simple utility that I've found to work perfectly for this is SnapzPro X from Ambrosia Software. This is a screen capture utility that can also “capture” video as it streams on your screen. As long as the video is streaming in high quality, this utility will capture the video at equally high quality. I've used this to capture streaming video for a number of real DPS projects, and it works great. Of course, you only want to do this when you or your company own the content that you are streaming and capturing.