From the NLI website.
"I understand I have signed this NLI with the institution and not for a particular sport or coach. If a coach leaves the institution or the sports program (e.g., not retained, resigns), I remain bound by the provisions of this NLI. I understand it is not uncommon for a coach to leave his or her coaching position."
Porter is still bound to UW until they let him go.
http://www.nationalletter.org/nliProvisions/coachingChange.html