This question has been answered by donshakespeare. See the first response.
tinymce.init({ selector: "...", plugins: 'link image code', convert_urls: false });
Ext.extend(TinyMCERTE.Tiny,Ext.Component,{ cfg: { selector: '#ta' ,document_base_url: MODx.config.base_url ,file_browser_callback_types: 'file image media' }
Ext.extend(TinyMCERTE.Tiny,Ext.Component,{ cfg: { selector: '#ta' ,remove_script_host: false //add this line ,relative_urls: false //add this line ,document_base_url: MODx.config.base_url ,file_browser_callback_types: 'file image media' }