The folks running the fairgrounds campground will likely work with you on the fourteen day limit if you're involved with something associated with the University. Sure wouldn't hurt to give them a call to discuss it.
I think the schools transportation system, Wolfline, provides service to Carter Finley which isn't very far from the campground.
http://www2.acs.ncsu.edu/trans/wolfline/schedules.html
Maybe you'll have time to visit the Outer Banks (3-4 hours from Raleigh) for a day or two after the second week to keep things legit.
NCSU is a great school in a great town. Go Pack!!!