JMS Big Bang Tespia Open For All (?)

The law on that is quite clear - You have the right to disassemble whats on your own machine.
You do not have the right to connect to locations you've been explicitly denied access to.
The first is reverse engineering, the second is illegal intrusion. They are not comparable, this is not debatable.

If you have access to JMS and want to post extractions, that's one thing. Teaching people who do not have access to JMS, KMS, TMS, CMS or even GMS how to bypass those restrictions is not an acceptable subject matter.
For that matter neither is teaching people how to do their own extractions.

I will add that Japanese police could theoretically come after you for illegal access. The bureaucratic mess that would invoke would make it highly unrealistic though.