Raspberry Pi does not use open source hardware. The processor core (ARM) is proprietary. The GPU (VideoCore IV) is proprietary hardware, and even includes proprietary software in the form of microcode. And so on and so forth.
Open source hardware refers to the silicon itself using open source designs.
Indeed, Broadcom doesn't even allow you to buy their proprietary SoC (at least, last I checked), so you can't make a knock off RPi board, or integrate the SoC and peripherals into a custom application board. You need to use an RPi directly or get some other Cortex-A53 chip with a comparable architecture.
Open source hardware refers to both the system level design and the IC level design. Credit where it's due, Raspberry PI is open hardware on the system level. You are right that it is not open on the IC level.
Nonsense. It's not open at any level by normal definitions (although some of the software is open source). The Raspberry Pi is a wonderful thing. It's cheap and it works great...but it's not open.
The VC4 GPU is a lot worse than microcode! It's running the complete (proprietary) ThreadX operating system, regardless of what you choose to run on the ARM core.
You meant VPU, not GPU? The GPU is fully open.
Yes, I called the VC4 the GPU because the parent post (and many other resources) call it a GPU. But yes, it is the VPU.
No, but it is what RISC-V is! I'm really excited about RISC-V after reading Andrew Waterman's PhD thesis[0] on it from earlier today.
Will the US allow something like that happen? The future is developing towards hardware backdoors in all processors and this would make it really hard to implement such system. There is no way this is going to happen.