David 
11/03/2015
You can download the engine and use it for everything from game development, education, architecture, and visualization to VR, film and animation. When you ship a game or application, you pay a 5% royalty on gross revenue after the first $3,000 per product, per quarter. It’s a simple arrangement in which Epic, the developers of the engine, succeeds only when you succeed.
You get full access to all the technology Epic uses for its own games. The engine scales from indie projects to high-end blockbusters; it supports all the major platforms; and it includes 100% of the C++ source code. Epic’s goal is to give developers absolutely everything: whatever you require to build and ship your game, you can find it in UE4, source it in the Marketplace, or build it yourself – and then share it with others.
Beyond the tools and source, Unreal Engine 4 provides an entire ecosystem. Chat in the forums, add to the wiki, participate in the AnswerHub Q&A, and join collaborative development projects via GitHub. Buy content in the Marketplace, or build your own and sell it there.
To help you get started, the engine includes a large number of video tutorials and documentation, as well as ready-made game templates, samples, and content.
