when using the following markup (can paste this into showcase example dataTableDynamicColumns.xhtml):-
{code}
            <ace:checkboxButtons id="checkbox"
                                 mutuallyExclusive="false"
                                 value="#{dataTableDynamicColumns.selectedCheckboxes}"
                                 valueChangeListener="#{dataTableDynamicColumns.checkboxChange}"
                                 styleClass="checkboxes">
                <ace:ajax render="@form" execute="@this"/>
                <f:selectItems value="#{dataTableDynamicColumns.checkboxes}"/>
            </ace:checkboxButtons>
{code}
note that if you use several <f:selectItem with an itemValue and itemLabel, then the labels appear on the checkboxes. It is simply the use of the <f:selectItems> that shows no labels. A checkbox is rendered (see attached screenshot).