I'm a developer and I can say, their system is a piece of sh*t.

Documentation on Google Docs? Omg, just by accessing their site you can see that it's a completely amateur job.

They use a pre-made theme very poorly adapted to their needs. And, to finish it, it isn't a offerwall. It's a way to they earn from banner and popup advertisements, only that. They pay a small fraction from their earnings to site owners show their "offers".

About being a scammer, I don't know because I don't use that kind of crap.