@jimmy @VIPPER Not the greatest link (this guy actually believes that copying software is theft and that translating a program line-by-line to Rust doesn't make a derivative work) but it does at least does show that the code of the RT kernel certainly was not copy-pasted.

It seems possible that they looked at the kernel design and implemented a similar structure (which was later changed to be different too), but who cares, as they wrote free software and respected the users freedom and didn't write proprietary software.