Mythic Table is a free, open source VTT solution, currently in Kickstarter. The business model seems to be based on content market.
https://www.kickstarter.com/projects/mythictable/mythic-tableThe hottest virtual tabletop (VTT) is taking things to the next level. Mythic Table aims to deliver a quality, easy-to-use VTT that is flexible enough to cater to all your gaming needs. In partnership with World Anvil, and the Open Gaming Network, Mythic Table is expanding its functionality to provide game masters and homebrew creators a platform to buy and sell game assets.