Compress (software) based on Lempel–Ziv–Welch
History
The LZW algorithm used in compress was patented by Sperry Research Center in 1983. Terry Welch published an IEEE article on the algorithm in 1984, but failed to note that he had applied for a patent on the algorithm. Spencer Thomas of the University of Utah took this article and implemented compress in 1984, without realizing that a patent was pending on the LZW algorithm. The GIF image format also incorporated LZW compression in this way, and Unisys later claimed royalties on implementations of GIF. Joseph M. Orost led the team and worked with Thomas et al. to create the 'final' (4.0) version of compress and published it as free software to the 'net.sources' USENET group in 1985. U.S. Patent 4,558,302 was granted in 1985, and this is why compress could not be used without paying royalties to Sperry Research, which was eventually merged into Unisys. 
compress has fallen out of favor in particular user-groups because it makes use of the LZW algorithm, which was covered by a Unisys patent –  because of this, gzip and bzip2 increased in popularity on Linux-based operating systems due to their alternative algorithms, along with better file compression. compress has, however, maintained a presence on Unix and BSD systems and the compress and uncompress commands have also been ported to the IBM i operating system.The US LZW patent expired in 2003, so it is now in the public domain in the United States. All patents on the LZW worldwide have also expired (see Graphics Interchange Format#Unisys and LZW patent enforcement).
In the up-coming POSIX and Single Unix Specification revision, it is planned that DEFLATE algorithm used in gzip format be supported in those utilities.