You can launch the webOS YouTube player from your app in a separate card using code like:
launchYouTube: function(mediaURL)
{
var params = {
target: mediaURL,
direct: true
};
this.controller.serviceRequest('palm://com.palm.applicationManager', {
method:'launch',
parameters: {
'id': 'com.palm.app.youtube',
'params': params
});
}
The mediaURL parameter looks like "http://www.youtube.com/watch?v=_6U9YGDtSEs" depending on the video.
As best I can tell, the YouTube player does not support the sublaunch mechanism that allows it to be embedded as a new scene on your own app's stage.