An ex-beOS kernel engineer has made his own free operating system from scratch!

"Is the world ready for yet another Operating System? Travis Geiselbrecht, an ex-BeOS kernel engineer, seems to think so. He is actually the one who wrote the Linux ext2 filesystem add-on for BeOS. Recently he put up on his web site his personal Operating System, NewOS, with full source code, which was written from scratch. Currently runs on x86 and the Sega Dreamcast but he is planning ports for Alpha, SGI and Sun Blade machines in the near future."