[Marco van Herwaarden]

Again wrong, also in the US it is not needed to register a copyright.

From WikiPedia:

In all countries where the Berne Convention standards apply, copyright is automatic, and need not be obtained through official registration with any government office.

In 1989, the U.S. enacted the Berne Convention Implementation Act, amending the 1976 Copyright Act to conform to most of the provisions of the Berne Convention. As a result, the use of copyright notices has become optional to claim copyright, because the Berne Convention makes copyright automatic.[6] However, the lack of notice of copyright using these marks may have consequences in terms of reduced damages in an infringement lawsuit — using notices of this form may reduce the likelihood of a defense of "innocent infringement" being successful

PS The simple fact the an author does not respond to your request does not remove his copyrights.