UUnity Software Inc.

Unity gives developers a game engine and sells advertising inside what is built with it.

The engine became the standard for mobile and small studios: a substantial share of the games in the app stores is built on it. The developer subscription brings in little but creates what is genuinely valuable — access to the audience of all those games.

The second half is built on that: an advertising network showing ads inside games and helping studios find new players. It brings in more money and it was also the source of trouble — an attempt to change the engine's pricing terms provoked an open revolt among developers and cost the company its chief executive. Risks: developer trust and competition from ad platforms. The company pays no dividend.