For JSP support, Openfire uses various libraries (commons-el.jar, jasper-compiler.jar, jasper-runtime.jar, jsp-api.jar, jstl.jar) that were once taken from Jetty (6.x). The libraries in use are ten years old, and lack support for functionality that by nowadays standards isn't even considered 'up-to-date' any longer (taglibs, JSTL, EL). On top of that: Openfire has long ago migrated to Jetty 9.x, causing a mix of dependencies from various versions of Jetty in Openfire.
The JSP support libraries should be brought up-to-date. Note that this will require some tinkering to the JSP pages, if only to upgrade JSTL support to anything higher than 1.0. This starts by replacing taglib qualified by these URIs:
with taglibs qualified by these:
In most cases, this will be a drop-in replacement. However, the JSP compiler might behave a little different (probably will be more strict), which could require some additional tinkering.