Check with your school's Technology Transfer group. While it is true that Universities generally want control over everything created while you are working for them, most of the time the value to the University is not worth their time or trouble. If your work will generate actual revenue for the University (revenue that will actually offset the work involved in licensing and all that), they'll be very interested. If not, they will most likely leave it up to you to do with it what you will. At least that is how it works at my school.