The first was the Santa Cruz Operation, which made SCO Unix, a computer operating system, from the 1980's till 2000. In 2000 they sold their Unix holdings and renamed themselves Tarantella, Inc, and were eventally bought out by Sun Microsystems.
The second is The SCO Group, which until 2002 was known as Caldera International, but changed their name after acquiring the Later company's Unix system. They became very notorious in the computer world for their ongoing series of lawsuits and claims that they 'own' the Linux operating system, and that it illegally contains their source code. All of which is rather ironic considering that they were a respected Linux company for almost a decade before they began these actions.