are his prophecies condemned by the Church? Are we permitted to believe in them or no?
Believe in "them" or no?
Well, it depends on what "them" is.
Nostradamus as interpreted by John Doe? By John Q. Public? By the Weekly World News?
Straight-up Nostradamus is so cryptic it could be predicting just about anything. So we have hundreds of "interpreters" who interpret Nostradamus' quatrains to predict all sorts of things, most of which have not come to pass.
I'd say it's more of a waste of time than anything else. I've encountered MUCH better (Catholic) prophecies that are worth our attention and belief.
After all, if nonbelievers are given preternatural abilities (Edgar Cayce?), including prophecy, there is a good chance they're getting it from the devil.
The devil doesn't know the future. He's just a damn good guesser, because he is so intelligent and sees the thousands of causes behind everything. He *understands* how the butterfly flapping its wings in Tokyo creates a hurricane in the Carribean, and where that hurricane will go. He's a good weatherman.
We can guess things too, but our minds are so puny they can't guess anything "impressive" unless we're trying to impress a 2-year-old. Flip a light switch, and the lights go off! Haha, I knew that would happen, even though the little kid is giggling because it was unexpected.
But God alone knows the future -- what will happen based on man's free will. And I doubt He shares that knowledge with random unbelievers...