Here's the link for Unisys LZW / GIF patent licensing. I don't have one for IBM, who also have relevant patents. These patents (both companies) extend until sometime in 2003, so any unlicensed software which writes them is breaking the law (in the USA, and in treaty countries).

http://www.unisys.com/unisys/lzw/

Free the internet: use PNG instead.

Cheers