There are too many commercial embedded operating systems to list here, but if
Linux isn't to your liking, here are some other open source operating systems
which share some of the same benefits, and have been ported to embedded PowerPC
eCos is an open-source, royalty-free, highly configurable, application-specific
operating system ideal for embedded systems development. It is targeted at
high-volume applications in consumer electronics, telecommunications,
automotive, and other deeply embedded applications.
RTEMS is a real-time executive which provides a high performance environment
for embedded applications including a POSIX 1003.1b API, TCP/IP stack,
multitasking, debugging and filesystem support.