The purpose of the above applet is to show the force on a current loop in a magnetic field.
The magnetic field line is a by product.
So all the magnetic field line pass throught the current (event when magnet is off-axis).
That is the reason , the field line starts from the current loop.
If you just need to show magnetic field lines for a bar magnet, I can modify the code to create another simulation:
1. remove current loop and other.
2. let field line starts from N pole.