They may really be offering that much tokens for the people eligible. What you have to ask yourself though, is who determines the value of those tokens? If OpenGift alone set selling its price, and it cannot be sold anywhere and OpenGift wouldn't buy it back, how exactly do you determine its actual monetary worth? The answer is you don't.

They may very well be legitimate, but I wouldn't expect their tokens to be worth anywhere near as much as they claim on the open market.

You asked the correct question by asking why they would need a blockchain in the first place. They don't. That means it's unlikely to take off, and investing would probably be unwise.