Final answer:
SVR4 was developed by AT&T. It is a version of the UNIX operating system and included commercial and proprietary developments over time.
Step-by-step explanation:
SVR4, which stands for System V Release 4, was developed by AT&T. It is a version of the UNIX operating system that evolved from the original UNIX developed by researchers at AT&T Bell Labs. SVR4 encompasses various features from earlier versions of UNIX, some developed by AT&T and some from the University of California, Berkeley. Over time, UNIX became commercialized and proprietary versions were developed by various companies, but the core SVR4 was an initiative of AT&T and not Sun Microsystems, the University of California, Berkeley, or any other entity.