Unity uses Mono for scripting in their engine. As it runs on a variety of platforms where replacing the runtime (which is normally LGPL licensed) isn't possibl

Unity uses Mono for scripting in their engine. As it runs on a variety of platforms where replacing the runtime (which is normally LGPL licensed) isn't possible, I believe they have a commercial licensing agreement in place with Novell. I don't know what the terms are of that agreement.