I have checked your header.php and everything is ok (you only miss the call to bb_feed_head but it's probably a design choice cause you don't want feeds.) Answer me some questions:
1) The javascript is generated inside <head> (this is the most important part)? You will find var za_buttons = new Array(); etc. in the page source (command+u on a Mac, ctrl+u on windows)
2) Again from the generated html. The textarea used for writing new posts is in this form?
<textarea name="post_content" cols="50" rows="8" id="post_content" tabindex="3">
or something similar? id must be equal to "post_content". If it is something else you must change the CSS selector accordingly.
3) You have javascript active? My plugin doesn't function if you use NoScript or similar Firefox plugin cause it relies on jQuery.
Regarding zaerl Simple Registration I made a request and I will upload the plugin as soon as I have got a new SVN repository. That plugin is only a little joke that I made in three minutes for helping a user on the forum and I don't have future plans but if I get positive feedbacks I will implement the feature you requested.
Right now I am busy trying to finish the first content patch of zaerl Visibility and this is sucking away all my spare time (Visibility is a very complex plugin.)