[deerIRL]

It may have changed, but back when we were looking into Engines to use, Unity had a completely free license until you hit $100,00 in sales or wanted to remove the unity splash screen on app launch which costed a then flat $1500 licensing fee for the "Professional Edition".

[andechs]

Removing the splash screen for Unity is a feature - Unity has a pretty bad rep (perhaps undeservedly) because so much shovelware uses the engine.