In fact the option is available, but it is was hidden. As a A workaround (and for the crew: to see what's missing), a visitor can re-enable the missing input field by pasting the following into the browser's location field (address bar), thus replacing the URL, when the login page is shown:
javascript:void($("#openid_form > div:first").show())
(As an aside, the FAQ also seems to assume that this field is available; see "enter it into the text box on the login page (including the http://) and click the Login button" at How do I log in climatedeal.org?)
Some notes for those fixing this:
It is explicitly hidden by the following (and some more customisation) in the HTML of the login page:
$("body > div[class=container] > div[id=content] > div[id=mainbar] > div[class=page-description] > form[id=openid_form] > div:eq(0)").hide();
Re-enabling it also shows that the order of text and inputs needs some work. ;-)
Also beware of the link "new login" at one's own profile page. This is meant to add a secondary OpenID to one's account (just in case the provider of the primary OpenID existed but is offline). When clicking that, the climatedeal.org specific customisations claim:
You're currently not logged into climatedeal.org
Non-customised sites state something like:
You're currently a registered user. You can log in or out at any time using the OpenID you've already associated with your account.
Logging in again with a different OpenID will associate it with your accountnow no longer relevant.
(On some other site this "new login" has been renamed to "add openid".)
