In terms of Japanese, copyright (版権, Hanken) is the old name for copyright (著作権, Chosakuken), but unlike copyright under the current Copyright Law of Japan (著作権法), it refers to rights over books, etc., which are part of a work, and not to scripts, music, photographs, films, etc.
Contemporary Usage in Japanese Language
"Hanken" is now colloquially used to refer somewhat to copyright and trade mark rights.
For example, a person who holds the copyright to an anime work (such as an anime production company) is called a 'Hanken-moto' 版権元 (Rights-holder), a picture of an anime character published in an anime magazine is called a 'Hanken-e' 版権絵 (Copyrighted Picture) and character goods are called 'Hanken Goods' 版権グッズ (Copyright goods). In some cases, 'Hanken' has the same connotations as 'official' or 'authorised', indicating that the rights-holder was involved.
Doujin goods are usually unofficial, but at model sales events such as the Wonder Festival, temporary sales licences are obtained through negotiations with the rights holders. This licence is also called 'one-day Hanken' 一日版権 (one-day copyright) or 'same-day Hanken' 当日版権 (same-day copyright).
In the case of crossover works, characters and works that are not original to the crossover work are often referred to as 'Hanken characters' or 'Hanken works', in order to distinguish them from the original characters of the work and the original works derived from them. .
Usage on pixiv
The tag is often attached with the implication that "Hanken things = Derivative works / fanart". When an author who usually draws original works draws fan art, it is often tagged to distinguish it from the original illustration.
Naturally, the "copyright (Hanken)" tag is not used for works that are original to the author or the artist.
Contrary to the above example, it serves to indicate that the work is an (unofficial) fan work for which someone else holds the copyright.
In some cases, authors of primary works have established guidelines for derivative works / fan art.
E.g. Guidelines pages related to the derivative creation of Team Shanghai Alice's creations (English)
Aliases and Notational Variants
Derivative Work (二次創作), Fanart (ファンアート)
Copyrighted Work (版権作品), Copyrighted Object (版権物), Copyrighted Illustration (版権イラスト), Copyrighted Character (版権キャラ) Copyright Crossover (版権クロスオーバー)
版權 (Traditional Chinese notation)
版权 (Continental Chinese notation)