Complex sentence: Before IBM unbundled software from hardware in 1969, the operating system (and most other software) was included in the cost of the hardware; and a single vendor had complete responsibility for the entire system, hardware and software.
Split into simpler sentences: Before IBM unbundled software from hardware in 1969, the OS (and most other software) was included in the cost of the hardware. Each vendor had complete responsibility for the entire system, hardware and software.