Greenfence is a Platform economy or a Sharing economy. These terms have a range of meanings, but in our case it means the possibility of members on greenfence to buy and sell their goods and services on-line, and when this is done there are transaction fees that are remitted to greenfence as part of the transaction.
Like other platform economies, greenfence is free to join and share information and collaborate with customers and suppliers on-line. All of this is free. This is very much like Amazon or eBay, it is free to join these sites and publish content, but when you choose to transact business on-line then there are transaction fees.