> Is there a way to disable editing of the textarea, but still allow editing 
> of other fields in the entry? (e.g. Fixed Attributes Edit = Text)

I could add that option, but I don't know if it helps you (see below).

> Also, is the data entered in that field accessible through a variable like 
> $author? I tried $text, but that doesn't seem to work.

No, that won't work. Attributes are limite to some 500 characters, while the
text body is limited to 250000 characters. If you add $text to an attribute, it
would overflow or you would have to truncate the text, which I guess is not
good in both cases.

If you still want "Fixed attributes edit = text", please explain me you exact
case and I will consider implementing it.