The Trader Contest regulations say no scalping, how does Dukascopy define this timeframe wise.
Where does it say no scalping? Quote the sentence(s) here. The only mention of scalping on the Trader-Contest rules-page is to say that the dukascopy evaluation criteria is designed to neutralize the misbalances arising out of scalping but I think scalping is still allowed.
You have the set limitations of minimal distance for TP & SL. - 10 EUR/USD pips
Also You need to make a comment of the trade. When You are really scalping as usual You don't have a time to do it :)
Where it says there is no scalping allowed?
Excerpt from the "Contest philosophy" of the Trader Contest:
"Scalping and using high leverage are not welcome in the Contest. The set of rules was introduced to encourage predictability, explanations and the ability to reproduce (copy) the trades of the contestants. To ensure this, the rules of the contest contain specific trading conditions and restrictions. Also, one of the main ideas of the rules is to reduce possible cheating."
You can trade however you want. But scalping likely means that you would open and/or close a position using a market order. That would have a negative impact on your order quality points and in turn your position in the standings.