Amazon has released its own game engine, Lumberyard, for free.
Lumberyard is based upon the CryEngine, which Amazon purchased from developer Crytek in 2015 for a reported $50-$70 million.
Interestingly, fees only come into effect when a developer utilises Amazon Web Services (AWS) for multiplayer.
“Amazon Lumberyard is free,” reads the website, “including full source code. You can deeply customize Lumberyard for your team, vision, and project today, and for future projects in years to come. There are no seat fees, subscription fees, or requirements to share revenue. You only pay for the AWS services you choose to use.”