Apparently, "Haiku" is the name of the successor to the alternative BeOS OS project originally created by Jean-Louis Gassée, who was originally hired, and later fired, by then Apple CEO John Scully. At one point, BeOS actually competed with NeXT as a contender for a successor to the original Macintosh operating system.
According to the article,
"From the beginning, Apple has been a tech soap opera. For example, back in 1985, Apple CEO John Scully — hand picked by Steve Jobs to run the company — fired Steve Jobs. Then he brought in the flamboyant Apple France capo, Jean-Louis Gassée to run the Macintosh division.
"For his part, Jobs went off to found NeXT Computer and Pixar.
"Five years later, Gassée was also fired by Scully. Like Jobs, he decided to create a new operating system, BeOS, one built without the inherent flaws of the Windows and Mac OSes.
"As luck would have it, in 1997, Apple found itself in need of an operating system. Apple considered both BeOS and NeXT, but ultimately settled on the modern NeXT OS created by Jobs et al.
"While both BeOS and NeXT were modern, multitasking operating systems, Jobs’ NeXT was much more mature and brought with an existing developer ecosystem — it was the better choice. Of course, getting jobs as part of the deal, that was pure genius.
"Though Gassée tried to make a go of selling BeOS after losing out to Jobs and NeXT OS, the company ran out of funding. BeOS’ assets were sold Palm in 2001.
"Various commercial and open source projects have kept BeOS alive to varying degrees over the years under a number of different names. Today, the open source Haiku project carries the BeOS torch."