I think he wants clarifications at least on the meaning of some of the language in clause 6, such as "any portion of the Converted OGL Product Line, or any products that would be considered part of a Converted OGL Product Line (as reasonably determined by Wizards) pursuant to the OGL," "same or similar title, product line trademark, or contents".I'm curious about what "clarifications" Clark wants, and what difference they could make in regards to his decision not to use the GSL. Some of the legalese is rather opaque, I agree, but I'd think he'd want some changes, and not just clarifications, before he'd sign the License.
These seem to be the issues that most need settling to understand the implications of no backwards conversion, and the implications for JG IP that he is concerned about.
From other posts he has made I also think that Clark is curious about the implicaitons of 11.1, and in particular the extent to which it permits unilateral termination against a single party without the grounds specified in clauses 1, 5.4 and 6.3 having to be made out.
I also don't understand why you think that clarifications would not be adequate. Are you a lawyer or expressing some other sort of professional opinion? If you are, then I'm happy to defer to it (though I'd like to hear more about why you think Mistwell is wrong). But my intuitions run the other way. I don't know quite where the US stands in respect of the parol evidence rule, but I would have thought that evidence of mutual understanding of key terms could be led in any suit for breach of contract, or in any attempt by NG to set up the contract as a defence against an IP suit. And depending on the nature of any clarification and NG's reliance upon it, it could also set up an estoppel against WoTC.
Depending on the details of any clarifications made, any going back on them might also have legal implications in the areas of misleading conduct or negligent mis-statement. But that is getting far more speculative, especially given that my limited knowledge of these areas of law pertains to Australia and not the US.