It is probably similar to Office Student and Techers edition. The main reason MS sells the S&T version is to make money off of people that would otherwise have pirated Office for their school and personal home use. With the S&T Edition they don't even require the store to check and see if you are a student or a teacher before they sell it to you.
As long as you are using it for personal or school use, I wouldn't worry about MS coming after you. The big thing is that the academic and S&T versions are strictly licensed for non-commerical use, so if you use it at your office or business MS has every right to come after you legally and either make you pay fines or sign up for a nice expensive multi-year software subscription with them to make you all legit. As long as you aren't using the software in a business capacity, MS really doesn't care what you do with the S&T Editions.