Martin Dougiamas

You say you're using Apache, but the error is from IIS.  Are they running simultaneously perhaps?  Try turning IIS off.

That message was just added to the stable branch and probably shouldn't have been, because it is rather scary.   In fact it only applies if you use the Authorize.net plugin for credit card payments.   It has nothing to do with Paypal or any normal Moodle usage.

I've modified the message.

Themes in 1.5 had a complete overhaul.  See the documentation on themes for details.

Yes, it does take time to make nice templates, that's why we added the button to auto-generate some default templates to get people started without any editing.

The idea of the list on the side is that clicking on it should insert the template tags directly into the template. Unfortunately we haven't got this working within the normal HTML editor yet (it does work when you're in source mode!)

Using the HTML editor has benefits in that it's really easy to style all the fonts, insert arbitrary images etc.

I'd be very glad to see alternatives! Anything that produces a HTML output could be good.

1.6 for sure.   It requires database changes so it couldn't go in 1.5.3.