This article is from the misc.writing Writing FAQ, by Wendy Chatley Green email@example.com with numerous contributions by others.
There is no clearinghouse for pseudonyms. No one
assigns them nor does anyone keep track of them, with one
exception. Publishers who "own" a book series written by
contract writers under a standard author name (Mack Bolan
and Carolyn Keene are examples) will object to the use of
that name by someone else. In this case, the name is a
trademark of the series and not an indication of the
identity of the author.