BeOS
The operating system originally designed to run on the BeBox microcomputer. BeOS is good at both multitasking and real-time operation. It has a bash command shell, with ports of many GNU programs by Be, Inc. It has a GUI front end (not X). A C++ compiler is supplied with the machine, and there are rumours of other languages being ported in the future.
BeOs eventually became used on the x86 and standard PPC.
Be, Inc. went bankrupt in 1999, after releasing the last upgrade of BeOS (R5.0.3), and was sold to Palm.
Several groups are currently (2003) attempting to create an R6 version of the OS. The most likely to succeed are Yellowtab and OpenBeOS, which is likely to be renamed.