When is the line-out over?

Deon Fourie of the Stormers throws into a line-out. He throws in deep where Duane Vermeulen rises high to catch the ball. The  Stormers play the ball and immediately attack.

Not just as a nitpick, but as a matter of interest, when is this line-out over?

Law 19.9 BEGINNING AND ENDING A line-out
(a) line-out begins. The line-out begins when the ball leaves the hands of the player throwing it in.
(b) line-out ends. The line-out ends when the ball or a player carrying it leaves the line-out.
This includes the following:
When the ball is thrown, knocked or kicked out of the line-out, the line-out ends.
When the ball or a player carrying the ball moves into the area between the 5-metre line and the touchline, the line-out ends.
When a line-out player hands the ball to a player who is peeling off, the line-out ends.
When the ball is thrown beyond the 15-metre line, or when a player takes or puts it beyond that line, the line-out ends.
When a ruck or maul develops in a line-out, and all the feet of all the players in the ruck or maul move beyond the line of touch, the line-out ends.
When the ball becomes unplayable in a line-out, the line-out ends. Play restarts with a scrum.

Now watch Jimmy Cowan of the Highlanders who stands in the receiver position just inside the 15-metre line. He is entitled to do that.

When may he cross that line?

Law 19 DEFINITIONS
Receiver. The receiver is the player in position to catch the ball when line-out players pass or knock the ball back from the line-out. Any player may be the receiver but each team may have only one receiver at a line-out.
Players taking part in the line-out known as participating players. Players taking part in the line-out are the player who throws-in and an immediate opponent, the two players waiting to receive the ball from the line-out and the line-out players.

The receiver is a player participating in the line-out.

Law 19.8 (i) Where the receiver must stand. The receiver must stand at least 2 metres towards that player’s goal line from that player’s team-mates who are line-out players and between 5 and 15 metres from the touchline until the line-out begins.
Sanction: Free Kick on the 15-metre line

Cowan was standing in the right place. But remember he was participating in the line-out.

Law 19.14 OFFSIDE WHEN TAKING PART IN THE LINE-OUT
(e) No player of either team participating in the line-out may leave the line-out until it has ended.
Sanction: Penalty kick on the 15-metre line

Vermeulen catches the ball in the line-out before the ball goes beyond 15 metres. The line-out ends when he throws the ball from the line-out to Dewaldt Duvenhage, the Stormers' scrumhalf.

A line-out stretches from the 5-metre line to the 15-metre line. If Cowan steps infield over the 15-metre line before Vermeulen passes the ball out of the line-out, he has left the line-out before it is over and he is offside and liable to a penalty.

If he crosses the 15-metre line after Vermeulen has passed the ball, he is legal.