Nope. You don't have to use OpenID [1] on Wacktrap, even if you've got one assigned. If you've added your OpenID url to your Wacktrap 'My Account' profile, you've only gotta use it when you feel like it.
Remember, you've got options: you can always choose whether you're usin' your OpenID to log in, or your original Wacktrap username and password you set up at registration.
Done here? Just click the Question link again, to hide this answer text
Links:
[1] http://www.wacktrap.com/faq/what-optional-openid-log
[2] http://www.wacktrap.com/faqs/tech-stuff