"MUS" is not a recognized operating system abbreviation in common use. Operating systems are software programs that manage computer hardware and provide services for computer programs. Examples of well-known operating systems include Windows, macOS, Linux, and Unix. "MUS" does not correspond to any widely used operating system.

1. Android OS is a mobile operating system based on a modified version of the Linux kernel.

2. It is an open-source software, primarily designed for touchscreen mobile devices like smartphones and tablets.

1. An operating system is not HP.

2. The full name of HP is Hewlett-Packard. It is an American multinational information technology company that manufactures and sells computer hardware, software, and services.