saeco: but do you actualy lose a backgammon for a timeout even if it wasn't possible to lose one if the game was played till the end?

Not on all occasions. If you alredy moved a piece off the board, then you aren't going to lose a gammon I think, but if you didn't - well, then it's backgammon time. I lost 5 points in this triple gammon nack game on a time out for example:

Nackgammon (netvenus vs. Gordon Shumway)