The exchange rate 1BTCD=50KMD will be the same for all the period of the swap (1 year) ?
Basically yes, but the exchange rate will decrease slightly every day to account the 5% APR bitcoindark has. With this we ensure there won't be more BTCD than there are KMD reserved for the swap.
So apparently there isnt any difference partecipating the ICO (as i done) and buying now BTCD and wait the swap?
Yes, with both ways you get the same KMD coins.
Is there a github or some site where i can see the milestone completion for ICO site to be ready for BTCD swap? I think it would stop lots of question about when it will be ready.
For the ICO site there is not, but I can assure everyone that there is progress everyday and it's just a matter of time when it is finished.