What I say that is crazy, is the use of <list> in 2 ways, that I don't think that can be defined well with a DTD.

Uh? What about this:

  <!ELEMENT list (listitem+)>
  <!ATTLIST list type (numbered|unnumbered|plain) #REQUIRED>
  <!ELEMENT listitem (#PCDATA|list)*>
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This describes exactly the target XML

What you proposed would be:

  <!ELEMENT list (listitem|list)+>
  <!ATTLIST list type (numbered|unnumbered|plain) #REQUIRED>
  <!ELEMENT listitem (#PCDATA)>
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Once again this is not the usual, and recommended, way of structuring lists.

And if you read my previous posts, I think I agree with you that the typos need to be fixed.

Oh, and this debate is probably moot anyway, as Murugesan mentionned a DTD, that seems to be out of his control.