Here is all what the director seems to have said about the age limit (that is the same in the French school):

"I noticed in the past that we should not encourage too much age difference because it's harder then to form groups that work." (http://www.clubic.com/pro/emploi-informatique.clubic.com/act...)

"42 indeed focuses first on the 18-30. We think about other people with care, but we already initially have much to do." (http://www.vousnousils.fr/2013/04/12/nicolas-sadirac-l%E2%80...)