I think it's a difference in what one considers to be "the API". Linux is very much to the de facto API side, whereas some other project might be more one the d

I think it's a difference in what one considers to be "the API". Linux is very much to the de facto API side, whereas some other project might be more one the de jure API side with a rigid specification and allowing any change within that. Most things are probably somewhere between the two.