[License-discuss] Can copyrights be abandoned to the public domain?

[Ben Tilly]

Based on http://www.linuxjournal.com/article/6225 and similar
articles, I'd long believed that a declaration that you were
abandoning copyright was a meaningless farce.

Then by accident today I ran across http://cr.yp.to/publicdomain.html
which claims the opposite, and cites actual court decisions as
evidence.

Is D. J. Bernstein out of his depth here, or does he have a valid point?