Epic Games announced today that Unreal Engine 4 will be free to use for games, applications, projects and more.
According to the official site:
We give you everything so you can build anything. You get all tools, all features, all platforms, all source code, complete projects, sample content, regular updates and bug fixes.
The 5% royalty starts after the first $3,000 of revenue per product per quarter. Pay no royalty for film projects, contracting and consulting projects such as architecture, simulation and visualization.
This move might be just what the engine needs to get more developers on board with using it this generation. For more information and to download the engine itself, check out the official page here.