Mike Milinkovich noted on the EG mailing list:
IANAL, but I think that one difference between non-assertion and royalty-free is that if we go non-assertion, the patent retaliation approach that we had previously discussed would no longer work. If royalty-free patent licenses are granted, you have something to revoke if someone sues for patent infringement. However, I personally have yet to see language that provides the equivalent if you use non-assertion.
This may not be a big deal, but I just wanted to make sure that we all understand that if we go non-assertion, then we may be losing the ability to use the termination of patent licenses as a defense against litigation.