I'm going to clue you in on two of the most popular game engines that people use in the industry, Unity and Unreal Engine.

Popular game engine Unity announced a “Runtime Fee” policy on Sept. 12 that, starting Jan. 1, would incur a fee upon developers each time a game utilizing Unity was downloaded.

Bossa Studios, the company behind Worlds Adrift, and Spilt Milk Studios, an indie outfit working on a top-down space adventure called Lazarus, had both released games using Unity and SpatialOS.