BeOS was an OS developed to run on the BeBox hardware, a PowerPC based machine. The OS was first released in October 1995 for use on the AT&T Hobbit, and later moved over to the PowerPC platform the next year. A Intel x86 port of the OS began in March 1998 with version R3. The last version released was R5.1 in November 2001 for x86 only. This OS was meant to be used for multimedia applications. It is POSIX compatible but is not a UNIX derived operating system (Windows is actually POSIX complient also).
Be was purchased by Palm (later acquired by HP), and the OS was abandoned. Former Be developers took the source code for 5.1 and created Zeta, which ceased distribution due to legal concerns. A clean room reimplementation of this OS is Haiku, which is open source and currently under development.
Professional audio recorders still sold run modified versions of BeOS still, such as the iZ technology RADAR 24 and RADAR V.