//TINYMCE editor
var MOSSBASIC = {
    theme: "advanced",
    theme_advanced_resizing: true,
    theme_advanced_path: false,
    plugins: "advlink,directionality",
    theme_advanced_buttons1: "fontselect, fontsizeselect, formatselect, |, bold, italic, underline, |, justifyleft, justifycenter, justifyright, |, numlist, bullist, link, unlink, |, code", 
    theme_advanced_buttons2: "", 
    theme_advanced_buttons3: "", 
    theme_advanced_toolbar_location: "top", 
    theme_advanced_toolbar_align: "left", 
    theme_advanced_statusbar_location: "bottom", 
    extended_valid_elements: "a[name|href|target|title|onclick], img[class|src|border=0|alt|title|hspace|vspace|width|height|align|onmouseover|onmouseout|name], hr[class|width|size|noshade], font[face|size|color|style], span[class|align|style], kbd, code", 
    relative_urls: false
};
 
var MOSSFULL = {
    theme: "advanced",
    theme_advanced_resizing: true,
    theme_advanced_path: false,
    plugins: "table,advimage,advlink,searchreplace,contextmenu,directionality,xhtmlxtras",
 
    theme_advanced_buttons1: "save, newdocument, |, bold, italic, underline, strikethrough, |, justifyleft, justifycenter, justifyright, justifyfull, |, styleselect, formatselect, fontselect, fontsizeselect", 
    theme_advanced_buttons2: "cut, copy, paste, pastetext, pasteword, |, search, replace, |, bullist, numlist, |, outdent, indent, blockquote, |, undo, redo, |, link, unlink, anchor, image, cleanup, help, code, |, insertdate, inserttime, preview, |, forecolor, backcolor", 
    theme_advanced_buttons3: "tablecontrols, |, hr, removeformat, visualaid, |, sub, sup, |, charmap, emotions, iespell, media, advhr, |, print, |, ltr, rtl, |, fullscreen, |, insertlayer, moveforward, movebackward, absolute, |, styleprops, spellchecker, |, cite, abbr, acronym, del, ins, attribs, |, visualchars, nonbreaking, template, blockquote, pagebreak, |, insertfile, insertimage", 
 
    theme_advanced_toolbar_location: "top",
    theme_advanced_toolbar_align: "left",
    theme_advanced_statusbar_location: "bottom",
    extended_valid_elements: "a[name|href|target|title|onclick], img[class|src|border=0|alt|title|hspace|vspace|width|height|align|onmouseover|onmouseout|name], hr[class|width|size|noshade], font[face|size|color|style], span[class|align|style], kbd, code", 
    relative_urls: false
};
 
var head = document.getElementsByTagName("head")[0]
script = document.createElement('script');
script.id = 'tinymceScript';
script.type = 'text/javascript';
head.appendChild(script);
script.src = '/_layouts/3082/tinymce/jscripts/tiny_mce/tiny_mce.js';
 
function ctv_enableTinyMce() {
    if (getCookie('ctvPortalTinyMCESafariDisable')) {
        return;
    }
 
    var rx = /RTE_ConvertTextAreaToRichEdit\("(\w+)"/;
    var as = document.getElementsByTagName("script");
    var enableForPage = false;
    for (i = 0; i < as.length; i++) {
        var st = as[i].text;
        if (rx.test(st)) {
            var ctlid = rx.exec(st)[1];
            if (tinymce.isWebKit && !enableForPage) {
                if (!confirm('TinyMCE support for Safari is experimental. Would you like to load it?\n\nClicking cancel will prevent this dialog from appearing for the rest of your SharePoint session.')) {
                    setCookie('ctvPortalTinyMCESafariDisable', true); //set a cookie to not load tinymce for this session
                    return;
                } else {
                    enableForPage = true;
                }
            }
            if (st.indexOf('FullHtml') >= 0) {
                tinyMCE.init(MOSSFULL);
            } else {
                tinyMCE.init(MOSSBASIC);
            }
            tinyMCE.execCommand("mceAddControl", false, ctlid);
        }
    }
}
_spBodyOnLoadFunctionNames.push('ctv_enableTinyMce');
 
function getCookie(name) {
    var start = document.cookie.indexOf(name + "=");
    var len = start + name.length + 1;
    if ((!start) && (name != document.cookie.substring(0, name.length))) {
        return null;
    }
    if (start == -1) return null;
    var end = document.cookie.indexOf(';', len);
    if (end == -1) end = document.cookie.length;
    return unescape(document.cookie.substring(len, end));
}
function setCookie(name, value, expires, path, domain, secure) {
    var today = new Date();
    today.setTime(today.getTime());
    if (expires) {
        expires = expires * 1000 * 60 * 60 * 24;
    }
    var expires_date = new Date(today.getTime() + (expires));
    document.cookie = name + '=' + escape(value) +
             ((expires) ? ';expires=' + expires_date.toGMTString() : '') + //expires.toGMTString()
             ((path) ? ';path=' + path : '') +
             ((domain) ? ';domain=' + domain : '') +
             ((secure) ? ';secure' : '');
}

Para NON_IE.JS (navegadores no IE), solamente hace falta quitar o comentar la linea:

_spBodyOnLoadFunctionNames.push('ctv_enableTinyMce');