The source article is way more informative: <a href="http://web.mit.edu/newsoffice/2011/language-from-games-0712.html" rel="nofollow">http://web.mit.edu/newsoffice/2011/language-from-games-0712....</a>
According the the paper, they used Freeciv, because it is open source and they could modify the source code. Their source code is available here:<p><a href="http://groups.csail.mit.edu/rbg/code/civ/" rel="nofollow">http://groups.csail.mit.edu/rbg/code/civ/</a>
How do you know the manual affected how well the computer played? IMHO Put a machine learning algorithm into playing enough games and it isn't so unreasonable it would do better than the default AI on at least some games.<p>They need a control where the computer doesn't have access to a manual and compare to that.