Silicon Graphics has seen fit to allow us to give this work away. It is free. There is no support or guarantee of any sort as to its operations, correctness, or whatever. If you do anything useful with all or parts of it you need to honor the copyright notices. It would also be nice to be acknowledged.
The LZW algorithm is derived from the compress program (the proper attribution is included in the source code). The Group 3 fax stuff originated as code from Jef Poskanzer, but has since been rewritten several times. The latest version uses an algorithm from Frank Cringle -- consult libtiff/mkg3states.c and libtiff/tif_fax3.h for further information. The JPEG support was written by Tom Lane and is dependent on the excellent work of Tom Lane and the Independent JPEG Group (IJG) who distribute their work under friendly licensing similar to this software. Joris Van Damme implemented the robust Old JPEG decoder (as included in libtiff since version 3.9.0, there was another Old JPEG module in older releases, which was incomplete and unsuitable for many existing images of that format). JBIG module was written by Lee Howard and depends on JBIG library from the Markus Kuhn. Many other people have by now helped with bug fixes and code; a few of the more persistent contributors have been:
Bjorn P. Brox Dan McCoy J.T. Conklin Richard Minner Frank D. Cringle Richard Mlynarik Soren Pingel Dalsgaard Niles Ritter Steve Johnson Karsten Spang Tom Lane Peter Smith Brent Roman Mike Welles Frank Warmerdam Greg Ward Stanislav Brabec Roman Shpount Peter Skarpetis Arvan Pritchard Bernt Herd Joseph Orost Phil Beffery Ivo Penzar Francois Dagand Albert Chin-A-Young Bruce A. Mallett Dwight Kelly Andrey Kiselev Ross Finlayson Dmitry V. Levin Bob Friesenhahn Lee Howard Joris Van Damme Tavis Ormandy Richard Nolde Even Rouault(my apology to anyone that was inadvertently not listed.)
Copyright (c) 1988-1997 Sam Leffler Copyright (c) 1991-1997 Silicon Graphics, Inc. Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that (i) the above copyright notices and this permission notice appear in all copies of the software and related documentation, and (ii) the names of Sam Leffler and Silicon Graphics may not be used in any advertising or publicity relating to the software without the specific, prior written permission of Sam Leffler and Silicon Graphics. THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.