Are these considered as dividends or It's actually POS? I just want to know If this is usury-based system or in other words, why are people rewarded and from where the tokens are coming from?
It's more like dividends. New GAS is generated with every new block and proportionally distributed between all NEO holders. This will continue until total supply of GAS (100000000) is reached. Moreover, there are several different types of transaction fees in NEO protocol. All of them are paid in GAS. Some of these transactions fees are collected by bookkeeping nodes (these are all set to zero right now, so bookkeeping nodes don't actually make any money), while other fees are redistributed back to all NEO holders in the same as newly generated GAS.