Every Raspberry Pi ships with a closed source OS, ThreadX, that boots Linux, BTW.
It's MIT licensed now, which isn't particularly useful when it comes to Pi (there's some Broadcom crap in that boot loader so it won't be open sourced) but otherwise is kind of interesting.
https://github.com/eclipse-threadx
It's MIT licensed now, which isn't particularly useful when it comes to Pi (there's some Broadcom crap in that boot loader so it won't be open sourced) but otherwise is kind of interesting.
https://github.com/eclipse-threadx