Hi Sylvain and everyone else who is wondering (I was asked a few times):
The answer is: the first prize is a scholarship to Wikimania 2015 in Mexico City. There should be two additional cash prizes (2nd and 3rd place), however, their size will depend on the amount we need for the first prize. I.e., if the first prize is American-based (for example), it will be cheaper to fly them to Mexico City than if they are Europe-based, for example. Therefore the exact sum will only be known after the winner is decided. If the scholarship will be very cheap, we will also be able to give small prizes to the 4th-10th places (can't promise).
In general: we sincerely apologize for the delay in this procedure; we've been working hard on getting the grant from WMF and were only able to overcome the bureaucratic hurdles (not the WMF's fault, to be fair) recently.