Its nothing to do with lawyers, and everything to do with the fact that Mongoose is the rightful license holder, and so it just wouldn't be professional to allow the Hawkmoon monograph into any form of circulation.
None. In my opinion Gareth Hanrahan did a great job on the MRQ1 version of Hawkmoon and Mongoose may want to Legendify that at some future date. My take on it would just muddy the waters.