Public domain?

I wouldn't think it is since it's being re-released in theatres.

Apparently I was wrong. I found it at this public domain movie site.
http://imovies.blogspot.com/2007/06/grapes-of-wrath-1940.html?m=1

Movies this old should all be public domain by now. It's had enough time to make its money.

No, it isn't. The studio renewed their copyright on it.