UNO alumni who join the UNO Alumni Association are eligible for library borrowing privileges. The Alumni membership card becomes your library card. The UNO Alumni Association has information about joining posted here.
You could also join the University Library Friends, a membership organization which supports Criss Library, and whose members are also eligible for library borrowing privileges. Information about the University Library Friends is posted here. Membership in the University Library Friends is $25.00 per year.