From Peter Janzen:

In September 2010, IBM contributed the XPages Extension Library (ExtLib) to OpenNTF. The community's response to the ExtLib has been overwhelmingly positive, as it greatly improves developer productivity when building applications with XPages.  Since the initial release of the ExtLib over a year ago, there haves been more than 40 releases delivered to OpenNTF. These releases have focused on both improving quality as well delivering new features. While developers have embraced the functionality delivered by ExtLib on OpenNTF, the community has also requested it be supported by IBM.

On October 17th, 2011, IBM contributed a new release of the ExtLib to OpenNTF. This release not only continues to improve quality and add new features, but it also serves another purpose. It sets the stage for many of the controls and objects to become a supported set of features for Lotus Notes and Domino. In order for the library to be a supported set of features, it must meet IBM's quality requirements and non-functional standards in areas like globalization and accessibility. To meet these objectives, changes needed to be made to the library's existing controls and objects, and some of these changes break backward compatibility with the previous OpenNTF ExtLib releases. Every effort was made to minimize these changes as well as to simplify the process to make existing applications work with the changed controls and objects.

For applications that use previous versions of the ExtLib, a simple recompilation is required and will fix issues for most library controls and objects. Issues related to property name changes, will be reported by Designer. Moreover, the library documentation contains a list for all the changes. For developers who have use the library's mobile controls, these will need to be manually reworked as these controls have been redesigned. For Java developers who have built their own controls and objects which inherit from the library, changes to the xsp-config files mean that a manual rework is needed. Documentation on all changes will be provided.

From a technical standpoint, the OpenNTF delivery now contains two sets of plug-ins. First is the "extlib", containing all the controls/features to be added to the Lotus Notes/Domino product. The second set is "extlibx", which contains all the controls/features in the incubation phase. The assets from "extlibx" will eventually be pushed down to "extlib", when they are judged mature, stable and robust enough, and if there is a sufficient business case. This allows the IBM team to continue to quickly deliver innovation through open source, while including parts of it in future products.

We believe that making parts of the ExtLib a set of supported features for Lotus Notes and Domino is vitally important. It will provide XPages developers with a major infusion of functionality and remove barriers that may have prevented certain customers and partners from adopting ExtLib.