What is the purpose of the second wifi network on board (some?) B787 aircraft?
I think it has to do with the use of IPads by mainly the cabin crew, according to this article:

It also helps to identify customers quickly, and can be used to alert other staff of a passenger’s special meal or service requirements.

In order to have to crew communicating to each other via the IPad they need to be connected somehow, so I guess that the network you see is just linked to a locally hosted server such that all the IPads can acces the same data even if a crew member makes a change.