Hussie confirmed it in the authors notes for book three  

Was it the owner of Skaianet, a younger grandpa Harley?

Yes

Whoever the fuck you want. My current fav crack ship is Caliborn♠️Peridot

Because he’s stunted. Since Caliborn forced the take over of the cherub’s shared body, it was not allowed to mature properly so he’ll never hit cherub puberty

Jade’s passwords were to stop the trolls from talking to her out of order, like how Karkat would talk to John backwards and then sporadically, so their conversations weren’t in the same order.

Terezi’s passwords show you the effect of the retcon, what John goes back and does

Aranea states here that those of her blood type can sometimes have them naturally. 

Calliope told Roxy here.

Yes.

Gamzee isn’t a goditer but he is wearing the correct Bard attire. 

Since Skaianet made Sburb and Sburb was adapted from the technology found in the Frog Temple on Grandpa Harley’s island, it’s hinted that he has a connection to Skaianet or even founded it. It would also parallel Grandma English founding Skaianet in the post-scratch universe.