Well, according to wikipedia these patents have now expired:

"The US LZW patent expired on June 20, 2003.[18] The counterpart patents in the United Kingdom, France, Germany and Italy expired on June 18, 2004, the Japanese counterpart patents expired on June 20, 2004 and the counterpart Canadian patent expired on July 7, 2004.[18] Consequently, while Unisys has further patents and patent applications relating to improvements to the LZW technique,[18] the GIF format may now be used freely."

Full details at http://en.wikipedia.org/wiki/Graphic...rchange_Format in the patent section of that article.