Licenses

LZW	Compression LZW (Lempel-Ziv Welch) is used in GIF and TIFF (when using LZW compression). Unisys owns patent on this algorithm, so if you want to use one of mentioned formats, you have to buy a license from Unisys (which costs about 5000$ for typical user). Unisys never enforced patent against trivial user. Patent expires on 2003. Rumor has it that IBM also owns a patent covering GIF (or LZW) format, I don't know exactly :) More info can you find on http://www.unisys.com
JBIG	If you want to use JBIG format, you have to buy a license, because JBIG is patented format (info on http://www.ibm.com, http://www.jpeg.org).

NetPBM	Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. This software is provided "as is" without express or implied warranty.
LibTIFF	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.
LibPNG	Thanks to Glenn Randers-Pehrson and all contributors of LibPNG project. It's a great library!
LibJPEG	This software is based in part on the work of the Independent JPEG Group - the great JPEG library.
ZLib	This software is based in part on the work of Mark Adler and Jean-loup Gailly - the great LZ77 compression library: ZLib.
RLE	Source codes of library (Utah Raster Toolkit library) are available (eg. on ftp.iastate.edu/pub/utah-raster/)...
	This program also uses some lines of code from many free projects like ImageMagick and Graphics gems and NetPBM. Thank's to all, who created these projects :-)