It was very established ninth circuit case law at that time that APIs weren't copyrightable. This exact point came up today during oral arguments, with Oracle not denying it but instead saying that the terms "interface" and "API" weren't intended to apply to something so massive as the structure, sequence, and organization of the Java standard library.

Additionally, the contract is public. http://www.groklaw.net/pdf/USLsettlement.pdf Point 9C on page 14 has the university declaring that as far as they know, no AT&T IP is present in 4.4BSD, despite it clearly having a UNIX compatible API.