It's brought up a bit of an existential question in the scene however, it's not uncommon for teams to use their own engine, or engines coded by other teams, and assets of various sorts are frequently borrowed (but heavily remixed) and used in demos (famously photos of models are often turned into digital paintings used as filler scenes, but it extends to samples and other material).
So DEMO2 exists purely on its artistic merits, design and style without a great deal of technical work having been done by the team. So is it "ok" by the unwritten scene rules or does it challenge the scene to focus less on the technical merits of a piece and only on the artistic bits?