These are the patents the Netpbm maintainer knows about that relate to Netpbm. It is basically just information the maintainer has stumbled over at some point -- no search has been done. No licenses have been granted by patent owners to the maintainer of Netpbm. Therefore, if you need a patent to use something in Netpbm, you need your own license. A note about patents in general: A patent gives an inventor the exclusive right to make, sell, or use the invention. If you independently invent something without knowing that the patent holder already did, that makes no difference -- the patent holder still has the exclusive right. It makes no difference if you give the original inventor credit. The patent applies to a method, not its expression, so writing a program from scratch to implement a certain method is still a patent infringement. Infringing a patent is not a crime per se, but to the extent that it costs the patent holder money, the infringer has to make it up. The original purpose of patents is probably perverted when patents are applied to things you implement in computer programs. This is one of the Free Software Foundation's causes. See . The Jbigtopnm and Pnmtojbig programs use arithmetic coding patents and other patents covering various aspects of the "front end." JPEG patents ------------ The Pnmtojpeg and possibly Jpegtopnm programs in some cases may use the arithmetic coding patents owned by IBM, AT&T, and Mitsubishi. There is difference of opinion on whether they do. Forgent owns a patent it believes covers JPEG compression. This patent was virtually unknown before July 2002, when Forgent began to enforce it. It has successfully enforced it against two companies (Sony and an unnamed Japanese digital camera maker), but without court ruling. This patent, U.S. Patent No. 4,698,672, expires in 2006. Philips and Lucent Technologies also own patents they claim cover JPEG. The following Netpbm components may be restricted by these patents: Jpegtopnm, Pnmtojpeg, Ppmtompeg, Tifftopnm, Pnmtotiff. These all do their JPEG work via a JPEG library not distributed with Netpbm. Your JPEG-related liability for using Netpbm is limited to your liability for using your JPEG library. Note that it is possible to use Ppmtompeg without involving JPEG and to build it without the ability to involve JPEG. The next best alternative to JPEG is probably PNG and maybe JBIG for bilevel (black and white) images. http://burnalljpegs.org contains information on this issue. MPEG patents ------------ The original University of California distribution of the Ppmtompeg code contains this statement in a README file: ... patents are held by several companies on various aspects of the MPEG video standard. Companies or individuals who want to develop commercial products that include this code must acquire licenses from these companies. For information on licensing, see Appendix F in the standard. Expired LZW patents ------------------- Unisys owns patents on LZW compression, which is used by Ppmtogif, and maybe on LZW decompression, which is used by Giftopnm. IBM also owns a patent that may cover the GIF tools. Unisys offers a license of the patent for trivial use for $5000. Its U.S. patent (Number 4,558,302) expired June 20, 2003. In most of Europe, the patent expired June 18, 2004. In Japan, it was June 20, 2004 and in Canada, July 7, 2004. IBM's U.S. patent expired August 11, 2006. Neither company has ever enforced the patent against trivial users of it. is an article dated April 18, 2000 on the issue. http://www.unisys.com/about__unisys/lzw/> is Unisys' view of the matter. For information from another perspective, see . The following Netpbm components may be restricted by these patents: Ppmtogif, Giftopnm. A good substitute for GIF if the patents are a problem is PNG (see pngtopnm, pnmtopng), which was developed with a primary purpose of not using any patented technology. You can also use the -nolzw option on ppmtogif to avoid using the LZW patent. The images so generated are larger than traditional LZW-compressed GIFs, but any GIF decoder can decode them just the same.