TIBCO just released its PageBus publish-and-subscribe message bus as open source. And no wonder: the company is under assault from open source projects/vendors like MuleSource (whose EVP of Sales used to work for TIBCO - funny these Oedipal complexes we have in the open source world :-), Talend, etc.
PageBus goes hand-in-hand with the OpenAjax Alliance work that TIBCO has done. It's a good start for TIBCO, though shows that it's still guarding its crown jewels. Give it time. In the meantime, here's what PageBus does:
What does this mean? It means that PageBus can help developers simplify AJAX development. Developers can focus on publish-and-subscribe APIs rather than point-to-point integrations between components. Mashing up, in short, becomes much easier.
PageBus is licensed under a BSD license.