There is no special patent threat to GIF format nowadays as far as we know; the patents that were used to attack GIF have expired. Nonetheless, this article will remain pertinent as long as programs can be forbidden by patents, since the same sorts of things could happen in any area of computing. See our web site policies regarding GIFs, and our web guidelines.
There are no GIFs on the GNU web site because of the patents (Unisys and IBM) covering the LZW compression algorithm which is used in making GIF files. These patents make it impossible to have free software to generate proper GIFs. They also apply to the compress program, which is why GNU does not use it or its format.
Unisys and IBM both applied for patents in 1983. Unisys (and perhaps IBM) applied for these patents in a number of countries. Of the places whose patent databases we were able to search, the latest expiration date seems to be 1 October 2006. 1 Until then, anyone who releases a free program for making GIF files is likely to be sued. We don't know any reason to think that the patent owners would lose these lawsuits.
If we released such a program, Unisys and IBM might think it wiser (for public relations reasons) not to sue a charity like the FSF. They could instead sue the users of the program, including the companies who redistribute GNU software. We feel it would not be responsible behavior for us to set up this situation.
Many people think that Unisys has given permission for distributing free software to make GIF format. Unfortunately that is not what Unisys has actually done. Here is what Unisys actually said about the matter in 1995:
Unisys does not require licensing, or fees to be paid, for non-commercial, non-profit GIF-based applications, including those for use on the on-line services. Concerning developers of software for the Internet network, the same principle applies. Unisys will not pursue previous inadvertent infringement by developers producing versions of software products for the Internet prior to 1995. The company does not require licensing, or fees to be paid for non-commercial, non-profit offerings on the Internet, including “Freeware”.
Unfortunately, this doesn't permit free software which can be used in a free operating system such as GNU. It also does not permit at all the use of LZW for other purposes such as compression of files. This is why we think it is still best to reject LZW, and switch to alternatives such as GNU Gzip and PNG.
Commercial redistribution of free software is very important, and we want the GNU system as a whole to be redistributed commercially. This means we can't add a GIF-generating program to GNU, not under the Unisys terms.
The Free Software Foundation is a non-commercial, non-profit organization, so strictly speaking the income from our sales of CD-ROMs is not “profit”. Perhaps this means we could include a GIF program on our CD-ROM and claim to be acting within the scope of the Unisys permission—or perhaps not. But since we know that other redistributors of GNU would be unable to include it, doing this would not be very useful.
Shortly after Unisys made its announcement, when the net in general was reassured thinking that Unisys had given permission for free GIF-generating software, we wrote to the Unisys legal department asking for clarification of these issues. We did not receive a response.
Even if Unisys really did give permission for free software to generate GIFs, we would still have to deal with the IBM patent. Both the IBM and the Unisys patents cover the same “invention”—the LZW compression algorithm. (This could reflect an error on the part of the US Patent and Trademark Office, which is famous for incompetence and poor judgment.)
Decoding GIFs is a different issue. The Unisys and IBM patents are both written in such a way that they do not apply to a program which can only uncompress LZW format and cannot compress. Therefore we can and will include support for displaying GIF files in GNU software.
Given this situation, we could still include GIF files in our web pages if we wanted to. Many other people would be happy to generate them for us, and we would not be sued for having GIF files on our server.
But we feel that if we can't distribute the software to enable people to generate GIF files properly, then we should not have other people run such software for us. Besides, if we can't provide software in GNU to generate GIF files, we have to recommend an alternative. We ourselves should use the alternative that we recommend.
In 1999, Unisys had the following to say about the issue of their patent:
Unisys has frequently been asked whether a Unisys license is required in order to use LZW software obtained by downloading from the Internet or from other sources. The answer is simple. In all cases, a written license agreement or statement signed by an authorized Unisys representative is required from Unisys for all use, sale or distribution of any software (including so-called “freeware”) and/or hardware providing LZW conversion capability (for example, downloaded software).
With this statement, Unisys is trying to take back what they said in 1995 when they gave parts of the patent to the public. The legality of such a move is questionable.
A further issue is that the LZW patents—and computational idea patents in general—are an offense against the freedom of programmers generally, and all programmers need to work together to protect software from patents.
So even if we could find a solution to enable the free software community to generate GIFs, that isn't really a solution, not for the problem as a whole. The solution is switching to another format and not using GIF any more.
Therefore, we don't use GIF, and we hope you won't use it either.
It is possible to make non-compressed images that act like GIFs, in that they work with programs that decode GIF format. This can be done without infringing patents. These pseudo-GIFs are useful for some purposes.
It is also possible to create GIFs using a patent-free run length encoding but this doesn't achieve the compression that one normally expects in a GIF.
We decided not to use these pseudo-GIFs on our web site because they are not a satisfactory solution to the community's problem. They work, but they are very large. What the web needs is a patent-free compressed format, not large pseudo-GIFs.
The PNG format is a patent-free compressed format. We hope it will become widely supported; then we will use it. We do provide PNG versions of most of the images on this server.
For more information about the GIF patent problems, see the League for Programming Freedom GIF page. Through that page you can find more information about the problem of software patents in general.
There is a library called libungif that reads gif files and writes uncompressed gifs to circumvent the Unisys patent.
http://burnallgifs.org is a web site devoted to discouraging the use of GIF files on the web.
1. We were able to search the patent databases of the USA, Canada, Japan, and the European Union. The Unisys patent expired on 20 June 2003 in the USA, in Europe it expired on 18 June 2004, in Japan the patent expired on 20 June 2004 and in Canada it expired on 7 July 2004. The U.S. IBM patent expired 11 August 2006. The Software Freedom Law Center says that after 1 October 2006, there will be no significant patent claims interfering with the use of static GIFs.
Animated GIFs are a different story. We do not know what patents might cover them. However, we have not heard reports of threats against use of animated GIFs. Any software can be threatened by patents, but we have no reason to consider animated GIFs to be in particular danger — no particular reason to shun them.