system v release 5 was developed in 1997 by the santa cruz operation (sco) as a merger of sco openserver (an svr3-derivative) and unixware, with a focus on large-scale servers. it was released as sco unixware 7. sco's successor, the sco group, also based sco openserver 6 on svr5, but the codebase is not used by any other major developer or reseller.