Can Novell release Unix as free software?

actually, when Unix was initially written the law was not automatic copyrights to anything you wrote, you had to take specific actions to copyright things. For much of the Unix codebase those actions were not taken, and so it was not under copyright, by AT&T or anyone else.

Then there was the Berkley lawsuit, which showed that large portions of the Unix codebase was under copyright by Berkley, not by AT&T.

the situation of who owned what is _far_ from being clear, even before AT&T sold it.