The chair of Colgate's board of trustees explains the action in a letter on Colgate's web site:
http://www.colgate.edu/DesktopDefaul...6013&nwID=3190
or just go to
http://www.colgate.edu and look for the relevant news headline.
As I understand from the trustees' statement, fraternities that did not sell will not be recognized and students will not be able to live in those unrecognized houses.
And yes, Colgate is most assuredly private; it's also very hard to get into, expensive, and ranks high in the U.S. News and World Report listings of national liberal arts schools.