The DjVu.js Library (everything that is in library/src directory) is subject
to, and may be distributed under,
the GNU General Public License, Version 2.
Everything else in this repository (including the DjVu.js Viewer and the browser extension) is distributed under the terms of The Unlicense.
The choice of GNU GPL v2 for the library is conditioned by the fact DjVu.js contains some code fragments copied from DjVuLibre or Java DjVu libraries, which are distributed under this very license.
The DjVu.js Library isn't a port of DjVuLibre or Java DjVu, but the published specification of the DjVu format refers to DjVuLibre as the de facto standard of the DjVu format and advises to study its code. Also, some parts of DjVu codecs aren't described in details and can be gotten only from the source code of DjVuLibre.
Here I put all the copyright notices, which I found in the source files of both DjVuLibre and Java DjVu.
DjVuLibre-3.5
Copyright (c) 2002 Leon Bottou and Yann Le Cun.
Copyright (c) 2001 AT&T
DjVu (r) Reference Library (v. 3.5)
Copyright (c) 1999-2001 LizardTech, Inc. All Rights Reserved.
Java DjVu (r) (v. 0.8)
Copyright (c) 2004-2005 LizardTech, Inc. All Rights Reserved.