Openfire uses a custom taglib that is used in the admin console. It's definition lists its URI as http://www.igniterealtime.org/:
However, when used in JSPs, a different URI is used:
Although this appears to be not a problem for the JSPs that ship with Openfire itself, it does prevent the taglib from being used in plugins.
The URI designation in the tablib defintiion has been modified to reflect its usage ("admin").