You could have handled this at the beginning of the process by having the survey inform the students you can use the data for any purpose you choose. (Obviously, there would be research done on how to word the release.)
I neglected to get their email addresses when I created the survey so I can't ask permission, but would I run into any legal problems if I go ahead with this?
Now you want to violate the copyright of the authors in order to make a profit. By a strict reading, I'd say it would be a violation and all one has to do is to find an attorney and they would have a prima facie case against you to start litigation. Is it fair use? I don't know. You tell us after litigation.
When you are a Bear of Very Little Brain, and you Think of Things, you find sometimes that a Thing which seemed very Thingish inside you is quite different when it gets out into the open and has other people looking at it.
--W. T. Pooh (aka A. A. Milne)