When you say:
I don't want to monetize this application and turn this into a 'product'.
You're wrong. That's exactly what you want to do. That's exactly what you're planning to do.
There's nothing wrong with that. There's certainly nothing hypocritical about that. Yes, "most of the magic" was built by other people, but that's true of everything we do in life. Most of my professional tools were built by other people. A lot of them are products, but some are open-source projects. Linus Torvalds is a much smarter programmer than I, and he works a lot harder, and (thank god) I get to use his freely-available work without paying him, and then I get to charge money for doing so. Because Linus gave it to me for that very purpose! (And I'm very grateful.)
I'm saying this because you sound like someone who is used to thinking of his time as cheap -- and like you can't quite believe that this thing you've built is a "real" product. (Which it is; it sounds more real than 50% of the products on the web.) And I wouldn't want to see you do something silly, like price your product without considering the cost of (e.g.) your time. [1] You need to be paid for the development time you've put in, and for the maintenance time you're going to put in, and for the opportunity cost of keeping this thing alive instead of devoting all of your time to some other project. Otherwise, you will ultimately abandon this project and go do something else -- something that will make a profit for you, and pay you a living wage, and let you go to conferences and take people out on dates.
What I'm trying to say is: Embrace the fact that you're going into business, and take it seriously. [2] Don't undersell yourself or your product, and for god's sake don't price it at cost without paying the system administrator and the management team (i.e. yourself). Remember that it's really easy to lower an asking price and really hard to raise it afterwards. Test the market a little, see what competing products are charging, and go for it!
[1] For all I know $20 a year is overpriced for an app like yours. I don't know what your market is like, or your competition. But consider charging by the month instead and asking $9.99. -- or, at the very least, sell 6 month subscriptions at $29 per. (Think: semesters.) Don't make the free trial more than 30 days. Remember the possibility that many of your customers won't be repeat customers: Only a certain number of language students remain language students for years at a time, so it's not as if the cost of acquiring a customer can be amortized over ten years. Speaking of the cost of acquiring customers, don't forget to budget for the Google ads!
[2] If all this going-into-business stuff just sounds like too much trouble for you... don't go into business. Upload the code to Sourceforge or github and get on with your life. There's no shame in that, either. It happens all the time.