While the title "publish/subscribe infrastructure" sounds like a big framework, PageBus is actually delivered in a about 4k of Javascript file with just three public functions (subscribe, unsubscribe and publish) and six private ones.
Not everybody is impressed though. Matt Asay said it is understandable for Tibco to do some open-source considering that Tibco's core products is threatened by open source vendors like Taled and MuleSource. Matt summed the issue by saying that
It's a good start for TIBCO, though shows that it's still guarding its crown jewels. Give it time.Anyway, in order to futher publicize the PageBus release, Tibco also announced a contest for building the "world's largest mashup" - provided off course that large mushup uses Tibco's components, and hey It actually offers some nice prizes...
Putting Tibco's publicity efforts aside, the notion of providing publish/subsribe communication infrastructure on the client side is actually important for mashups and service UI integration. When create a UI which integrates several services you are likely to get few unconnected "portlets" - each representing the service it interacts with. To make the UI more, well, integrated, the next step is to start doing some point-to-point integration between the otherwise disparate components. integration components like PageBus, allows you to connect UI component in a loosely coupled way and prevent the integration spaghetti. You can also find the similar functionality in other environment that allow Client/Service application (vs. the indirect integration of Client/Server/Service). For instance the Composite Application Block from Microsoft support a component called the Event-Broker which provides similar functionality for smart-client mashups. PageBus brings this functionality to the Rich Internet Applications (RIA) realm.
It would be interesting to see if Pagebus will be a popular choice in upcoming RIA based mashups or will some other product come dominate this niche.