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Some history: Unisys and the GIF patent

Patents: I’ve just come across Tim Oren’s page on the Unisys GIF patent furore of 1994-5. Tim used to be VP of ‘Future Technology’ at CompuServe.

The GIF furore, in case you missed it, was one of the most far-ranging software patent debacles to date. Here’s what happened…

Compuserve was one of the biggest online services at the time. In 1987 they’d created GIF, an efficient image file format, for public use, with a very liberal license. As a result, everyone and their dog wrote software to read and write GIF files (including myself ;).

GIF, like many other tools of the time, used the LZW (Lempel-Ziv-Welch) file compression scheme, which had been widely published without any indication that it was considered proprietary. LZW was pretty much the de-facto standard for file compression in the early 90s, in the same way that ‘gzip’ is nowadays.

However — 7 years later, in 1994, Unisys suddenly announced that they had filed for, and eventually received, a patent on the LZW algorithm. As Tim wrote at the time, this was a ‘submarine’ patent. (Unisys had owned that patent since 1985, and pursued hardware licenses — but all and sundry believed that the patent didn’t cover software-only implementations.)

Unisys shook downbrought an infringement suit against Compuserve, who had published the GIF standard and implemented it widely in their software. Compuserve had ‘no recourse but to settle’.

(Interestingly, it appears that at the time, Unisys seemed to think that GIF decoders needed licenses as well — popular thinking nowadays is that only GIF encoders need licensing, but Unisys didn’t think so at that stage at least.)

There is a happy ending — thankfully, free software saved the day. ;)

As Tim writes, Thomas Boutell, Jean-loup Gailly and others came up with PNG; Jean-loup and Mark Adler wrote GZIP; and LZW was consigned to the dustbin of unusable technology for most new projects. Old projects, of course, had to go through some redesign pains to achieve the same goal.

BTW, it’s worth noting that, even though the Unisys patent has expired, it’s still not safe to dust off LZW. GNU (and others) believe that there’s another patent filed on the same algorithm independently by — guess who — IBM, which doesn’t expire until 11 August

  1. The thoroughly-competent USPTO strikes again ;)

The lesson: be careful when implementing published standards. Nowadays, the IETF requires that contributors disclose ‘the existence of any proprietary or intellectual property rights in the contribution that are reasonably and personally known to the contributor’. But in this case, the patent was owned by another body, Unisys, and the contributor (CIS) didn’t know that, so that wouldn’t have helped.

So, the real lesson: Just Say No to software patents ;)

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