odoo/addons/event_moodle/event_view.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>
        <record model="ir.ui.view" id="moodle_information">
            <field name="name">event.moodle.registration</field>
            <field name="model">event.registration</field>
            <field name="type">form</field>
            <field name="inherit_id" ref="event.view_event_registration_form" />
            <field name="arch" type="xml">
                <xpath expr="/form/notebook/page[@string='Extra Info']" position="after">
                    <page string="Moodle">
                        <field name="moodle_users" readonly='1' colspan="2"/>
                        <field name="moodle_user_password" readonly='1' colspan="2"/>
                    </page>
                </xpath>
            </field>
        </record>
    </data>
</openerp>