Universities are billion dollar organizations focused on their own financial growth. Many universities are private and obsessed with growth. There is no issue

Universities are billion dollar organizations focused on their own financial growth. Many universities are private and obsessed with growth. There is no issue with charging them to help on their mission. In fact, it's probably the only way to do so sustainably. If they like your tool enough, and you stopped working for them for free to do so, they would likely find the funds to get someone else to make it, while using your free labour like too many organizations do already in other ways. The other thing to look out for is brain rape. Academia will love to understand how you solved a problem in detail so either they can present it as their own, or imagine they could do it themselves. Consider if you are being meek or gun-shy, and how much of it is the desired behaviour of you.