I am very surprised that Joe had this kind of money for building a library.
Joe Paterno's salary is very low compared to other division 1 college football coaches. It almost seemed unfair to him with his kind of seniority and achievements. I think his base salary is about $500,000. His total salary including other compensations is definitely less than 1.5 million dollars in 2007 season. There were quite a few division 1 college football coaches make over 3 million dollars last year. Even in big10, his salary is in the average level.
Anyway, I don't think Paterno Library was donated by him. It is a library for honoring his coaching success. According to Penn State Library's web information, Joe and his wife helped raise 13.2 million dollars for the Paterno Library in 1993.