The Weekend of Code is about writing a program from Friday Evening until Sunday Morning which will be scored by several different criteria (usability, efficency, creativity, …). The best teams (up to 7 people) will be rewarded.
Allowed are programs of all kind in every programming language. But consider that a program written in Brainfuck may get better a score than a program in Java.
Beside the competition the exchange between the teams is also an important aspect.