It was called Rhapsody then, and work had started on it even before the ink was dry on the NeXT acquisition.

The rebranding to OS X was largely cosmetic from the command-line userland and underlying OS architecture's points of view, despite what the tech media often claimed about it at the time. OS X ported "Carbon" Mac OS 9 APIs to the new operating system; the Rhapsody strategy was either "Yellow Box" (former OpenStep, now Cocoa) runtime, or run in an emulation environment.