[LukeShu]

People are working on it. The biggest challenge is that it isn't "let's reverse engineer this ARM blob"--they have to reverse engineer the entire (VC4) architecture, and write an assembler for it. Most people think of the rPi as an ARM board; it's more helpful to think of it as a VideoCore IV board with an ARM co-processor tacked on. The stock "boot blob" isn't just a boot blob--it's actually an entire OS (ThreadX, I believe) that's running on the VC4 GPU, in parallel with whatever OS you load on the ARM CPU. Of course, you wouldn't need to re-implement all of the OS, but it does make reverse-engineering harder.

The people working on this like to hang out at #raspberrypi-internals on Freenode.

(Disclaimer: the last I looked into this was in January, before the Raspberry Pi 2 came out)

[sklogic]

It's not VC4 GPU, which is fully documented and fairly open. The bootloader runs on VPU, for which the reverse engineering is the only option, because there were no resources for doing anything sane with the official internal docs, when I checked last time. And Broadcom does not even own a compiler for this ISA. So, people had been officially encouraged to reverse engineer it.