For more information...

My source code - consider it to be GPL'ed.
To use the code, you need the Polya library, available here.
Craig Reynolds' boids
(Not) Evolving Collective Behaviors in Synthetic Fish - I didn't use this at all (I found it too late), but its on the same topic.
Teamwork in Genetic Programming - same as above, but he got results (using ants in a more complex environment).
The Gentic Programming Tutorial.
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