Copyright to the questions and answers across the stack exchange network is transferred to the for-profit Stack Exchange, Inc., so that might preclude usage due to the "and not for any direct or indirect commercial purpose or advantage" clause. However, all of the SE content is licensed as cc-wiki (CC-BY_SA), so in a sense it is free. Moreover, this site, along with many other elements of the SE network, has education as one of its goals.
While I used the COMET program as the basis for this question, this question is not specific to that program. There are many other sites that allow free use of those sites' copyrighted material for educational purposes but explicitly disallow such use for commercial advantage.