In the us, unpublished works created before 1978 are copyrighted until 70 years after the death of the author (Sweeden might be different though).

So you might be waiting a long time.

> he could release his "work output" and own the copyright on that

Probably not in the united States, but other countries (i know UK at the very least) this would be true. The united states requires "creative decisions" to grant copyright. Work output by itself doesn't count.

You could still distribute it, you just couldn't copyright it.