1) Allows communication via instant messaging between two copies of Radio. This could be used for instant outlining (the ability to share outlines you create in Radio instantly with people that subscribe), notification of updates to a weblog (instant news aggregation), and more. It also allows you to publish to your weblog via any supported IM client.
2) Build instant messaging bots. This means you can build applications in Radio that people can ask questions of via IM. For example, if you build a database of artist/album titles using Radio and connect it to this framework, people could input "Sinatra" via IM and get a list of albums he recorded.
3) It could, if there was a way to tap into the file attachment function of IM systems be a way to share file directories between subscribed desktops. This would be great for shared documents, photo albums, and multimedia directories. If you add a file to your shared desktop folder, everyone that subscribes to it would get it instantly.