In icefaces\component-metadata\src\main\resources\conf there are a bunch of xml files for the components, with <property-class>java.lang.Boolean</property-class> sections.

As well, in some of the components, the property getters and setters do not follow the JSF norm of:

public Boolean getProperty() {
    if (property!= null)
        return property;
    ValueBinding vb = getValueBinding("property");
    if (vb != null)
        return (Boolean) vb.getValue(getFacesContext());
    return Boolean.FALSE;
}
public void setProperty(Boolean property) {
    this.property = property;
}

Together, these create a problem for JSP applications that have components tags using these attributes with non-ValueBinding values.

Specifically, the expanded attribute on the panelAccordion component is one, but my searches found more instances of this issue. What's less known is if all of the other primitive attributes share this issue, like java.lang.Integer.