<h:selecBooleanCheckbox id="box" value="#{mybean.selecteditem.booleanvalue}"......>
<f:ajax execute="box" render="but" event="change" />
</h:selectBooleanCheckbox>

<h:commandButton id="but" action="someAction" value="someValue" disabled="#{!mybean.selecteditem.booleanvalue}" />

<p:ajax event="change" process="box" update="but"/>

<f:ajax ......render="id1 id2 id3" />

public class TestBean {

    private boolean chkBoxChecked;

    public boolean isChkBoxChecked() {
        return chkBoxChecked;
    }

    public boolean isBtnDisabled() {
        return !this.chkBoxChecked;
    }

    public void setChkBoxChecked(boolean chkBoxChecked) {
        this.chkBoxChecked = chkBoxChecked;
    }

}

<ui:composition xmlns="http://www.w3.org/1999/xhtml"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:a4j="http://richfaces.org/a4j"
    xmlns:rich="http://richfaces.org/rich"
    template="/WEB-INF/template/default.xhtml">

    <ui:define name="content">
        <h:form id="frmTest">
            <h:selectBooleanCheckbox id="chkBoolean" value="#{testBean.chkBoxChecked}">
                <a4j:support event="onclick" ajaxSingle="true" reRender="btnSubmit"/>
            </h:selectBooleanCheckbox>
            <h:commandButton id="btnSubmit" value="Submit" disabled="#{testBean.btnDisabled}"/>
        </h:form>
   </ui:define>
</ui:composition>

<ui:composition xmlns="http://www.w3.org/1999/xhtml"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:a4j="http://richfaces.org/a4j"
    xmlns:rich="http://richfaces.org/rich"
    template="/WEB-INF/template/default.xhtml">

    <ui:define name="head">
        <script type="text/javascript">
            window.onload = function() {
                btnSubmit = document.getElementById('btnSubmit');
                btnSubmit.disabled = #{testBean.btnDisabled};
            }
        </script>
    </ui:define>

    <ui:define name="content">
        <h:form id="frmTest" prependId="false">
            <h:selectBooleanCheckbox id="chkBoolean"
                onclick="btnSubmit.disabled = !this.checked;"
                value="#{testBean.chkBoxChecked}"/>
            <h:commandButton id="btnSubmit" value="Submit"/>
        </h:form>
    </ui:define>
</ui:composition>

<h:form id="myForm">
   <h:selectBooleanCheckbox id="check" onclick="document.getElementById('myForm:myButton').disable = !this.checked"/>

   <h:commandButton id="myButton" .../>
</h:form>

onclick="document.getElementById('myForm:myButton').disable = !document.getElementById('myForm:check').checked"

<script type="text/javascript">
   function checkClick(check) { document.getElementById('myForm:myButton').disable = check.checked; }
</script>
(...)
<h:selectBooleanCheckbox id="check" onclick="checkClick(this)"/>
(...)