I'm sorry, but i do not think imprimatur belongs in a discussion of words about censorship or banning books. An imprimatur is an endorsement of a book by the local bishop. A book can be published without the endorsement of a bishop. There are many books on the Catholic fiath without an imprimatur.

Associating the word "imprimatur" with censorship reinforces a prejudiced stereotype that the Catholic Church tries to withhold knowledge. In reality, it was the Catholic Church that started the university system.