> gaming for one, requires the source to be secret, or else you'll allow anyone to build and release the game easily and thus not recuperating costs of producti

> gaming for one, requires the source to be secret, or else you'll allow anyone to build and release the game easily and thus not recuperating costs of production. The engine is not the game, it's missing all the assets (3D models, textures, audio, scripts, etc). The assets don't need to be GPL-licensed. Most games use one of the few popular game engines: Unreal Engine, Source or Unity, which while not being open-source, are available to anyone and make it possible for anyone to build and release games with them. That doesn't stop them from making money.