Last Friday marked the demise of U.S. Patent #4,558,302, also known as the Lempel-Ziv-Welch data compression patent. Now you may have been blessedly unaware of the existence of this piece of IP, but you've certainly used it. LZW is the compression algorithm used in the GIF graphics format, on web sites far and wide, and the existence and enforcement of that patent by Unisys created the CompuServe GIF flap of 1994-5.

Why should I care, other than a general investors' interest in software patent law? Well, at the time I was VP of 'Future Technology' at CompuServe. Late in December 1994, a junior product manager who will go nameless posted a release regarding an LZW license-through from Unisys on CompuServe, and left town on holiday. A few days later I get an e-mail from a friend telling me all hell is breaking loose on the developers' mailing lists and news groups, and maybe I should look into it. That led to a late night call to the CEO, and spending part of my own vacation playing flack-without-portfolio and doing damage control.

All eventually ended up reasonably well considering the circumstances, and I was able to align CompuServe as a backer of the PNG graphics standard. For those who care about such things nine years later, the GIF24 'specification' that I was associated with at the time was always a stalking horse and never had an engineering team assigned. At the time it was announced, we were talking to the PNG group, and quietly funding an independent IP review of their design. When that came up positive, we used our PR clout to swing more attention towards PNG, having been convinced of the merits of free engineering open source.

So here's cheers to Thomas Boutell, Jean-loup Gailly, and the others who sweat out the PNG spec. And it gives me great pleasure to dance upon the grave of the late and unlamented US Pat. No. 4,558,302. Hopefully those who spent their time enforcing it will now have to find honest work.

Caveat, according to the original kuro5hin story, the following foreign versions of LZW remain in effect:

The European patent EP0,129,439 covers Germany, France, Britain and Italy and expires on the 18th June 2004.
The Canadian patent CA1,223,965 expires on the 6th June 2004.
The Japanese patents 2,123,602 and 2,610,084 expire on the 20th June 2004.

Though I doubt that much effort will be spent enforcing them at this point.
4:16:21 PM