Yes, widget creation calls are sent over the network. You can't assume that all apps will load interfaces from XML files. Most apps don't. I hope not. That would probably be too slow.
Programs look like normal programs.
Sorry for the spacing by the way. These can be run over the web, and anyone who can put together a web page can create a BlueBox app by combining various components. This rings my vapor bell big time. There are no downloads, and the technical details are vague to say the least. All of our software is open source.