Eh? They're still using original backgrounds when they could use the PS3 ones or whatever, and no voice? Doesn't seem like a very good decision to basically release an inferior version. :/ Also they release Higurashi 1 episode at a time, and Umineko 4 at a time? So many questions... I'd probably know the answers if I'd at all followed what Mangagamer does, but alas ¯\_(ツ)_/¯
Anyway, to answer your questions that seems to be precisely that same VN, with https://vndb.org/v2153 being the other 4 chapters. And IMO it's much better if you read Higurashi first, because otherwise there are a few minor references you won't pick up on and spoilers you might notice, but if you don't want to read Higurashi for whatever reason, Umineko stands on its own just fine.