Do I need to license GIF?

The LZW compression algorithm was covered by U.S. Patent 4,558,302, owned by Unisys Corporation. When CompuServe first developed the GIF format, they did not know that LZW was covered by a patent. In December 1994, after Unisys discovered that the newly popular file format used LZW compression, they announced that they would be seeking royalties on that patent; all commercial programs capable of producing GIF files would be required to pay a license fee to Unisys.