Great question! We explain how value is generated for GoodDollar G$ coins in this video https://www.youtube.com/watch?v=qNaKQrrA9Ew&t=3s.
If you are participating in the GoodDollar demo, you must note that demo G$ coins collected as part of the demo have no monetary value and cannot be exchanged for fiat currencies, cryptocurrencies, and / or goods and services.
The purpose of GoodDollar demo is to increase market awareness and quality assurance. You shall not attach any value to G$ demo coins and you are prohibited from using G$ demo coins for any purposes other than to access and use the GoodDollar’s demo-test software. Our Demo Agreement provides more information.