There's no such thing as free. Dave and his crew wouldn't blow 20M on this project if they didn't think there was a return of investment. The ROI is engine licenses and royalties.
Their engine could be demonstrated with simulated data but having real players is the best presentation.
They borrowed the idea from Guild Wars. GW isn't a true massively multiplayer game it is a glorified match-making lobby. But that's irrelevant. The engine was built and populated with free accounts all in the interest of demonstrating the power of the GW engine.