Yes it is dead if it breaks the goal line and is not good. I said that, but not too clearly, didn't want to get too complicated.
Since it is a scoring kick - it is not AUTOMATICALLY dead when it crosses the goal line - it is treated like a field goal when it comes to the goal line.
Once it breaks the plane:
If it still has a chance to be good, it is still alive.
If it is obviously no good (way wide or way short, for instance), it is dead when it breaks the plane of the goal line.
If it is way short and lands in the field of play:
It is dead if it breaks the plane of the goal line.
If caught or recovered by R in the field of play, it may be returned as any other free kick.
Oh - and if it actually crosses between the posts and above the crossbar, it is good and is worth three points.
