- releasing the source doesn't tell you what's on the chip.

- PSP is kind of "Ring ∞", so there would be no good outcome from providing general-purpose access to it. So, the keys will never be released.

- it's thusly not possible to map the signed (encrypted) firmware to the source.

- even if the source had a clearly documented "master off" in it, you can never know if the firmware's copy reads "master-except-if-A-and-B-say-C off" :(