Unisys Patent on Gif

http://www.freesoftwaremagazine.com/node/1772
- Unisys decided to make money from the GIF format image - they were going to go after developers of programs able to load and save gif.
- PNG file was invented as a reaction to Unisys' move; although it was never wildly successful, PNG did manage to make Unisys's threat very much irrelevant. Unisys took their time, but eventually realised that if they had seriously sued people over the GIF patent, the days of the GIF format would be over.
- What a mess it is to determine when a patent expires:
  - 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 employment of the GIF format..
- Is The PNG Format Successful