This demo isn't actually encrypted in the same way as the other PSN demos are.
The EBOOT format is the same as all the other PSN demos however it doesn't use a .RIF license file which allows the game to be shared (if you search google you will realize that Namco are also hosting the EBOOT on their site).
Because of this NP Decryptor fails with NpegOpen error 8 and refuses to decrypt the PSAR section of the EBOOT into an ISO. It is also possible and quite likely that even if there was a .RIF file that it would still fail because it may be in the newer EBOOT format used by many of the newer available demos which causes NP Decryptor to fail.