You're right. Pretty much all the low level stuff below the kernel in a pi is closed source.
Want your own custom boot rom so you can start up in half a second rather than the default 3 seconds before linux gets loaded? - sorry, we can't share the code for that with you, nor the specs for you to write it yourself!
That's not what they meant. Yes, anybody can write bare metal alternative to Linux ( at the very least by looking at the Linux codebase). But still that Pi 1541 depends on the bootcode.bin, fixup.dat and start.elf binary blobs, which the OP was complaining about.
It wasn’t clear to me what they meant. I’m not familiar with the details of boot.bin but my read of what GP was implying was you had to use the rapsbian kernel and drivers. Thanks for the information.
Want your own custom boot rom so you can start up in half a second rather than the default 3 seconds before linux gets loaded? - sorry, we can't share the code for that with you, nor the specs for you to write it yourself!