Their final deadline is May 15th. The IRS 990 form is one of the few sources of information the secretive foundation will now reveal, other than a bare-bones state required independent audit. The Foundation used to also publish an annual report with data on how much money went to athletics, etc. But since Paul Weinhold took over as CEO, that has been stopped.
Why the filing delays? I don’t know, the OSU Foundation always manages to get theirs in on time. Here is the UOFs 990 for last year, filed on the last possible day. These delays mean that the data on salaries and perqs for the Foundation’s top officials is almost 2 years old by the time it’s public. A few years ago, in response to complaints, the IRS tightened the rules on second extensions and required non-profits give an explanation for the delay. As you can see there’s there’s not much teeth behind that: