It can read unsigned code, but that doesn't do much for us with retail systems.
Nope. Not at all. That is an incorrect rumour.
The code IS signed. Judging by this unit I'd guess it's approximately SDK rev 0.14.21...maybe even a little bit earlier.
Normal developers can't import things to this is unit without a key guarded (
slightly lower) than the retail key. In order to import to the rev you NEED that key. It's actually pretty difficult for developers to get even from Nintendo.
There are 2 (main) keys for developer systems:
1- The SD importing key (given to most every developer, ONLY works on units with more recent revisions)
2- The NAND importing key (given to TRUSTED developers, can import things to any unit/rev)
I doubt this seller is including the NAND key, and much less the SDK, so GL to the buyer getting both of those.