I was thinking of something like yours for a while. But mine is more close to accent training for several different languages. I think you don't need to avoid m

I was thinking of something like yours for a while. But mine is more close to accent training for several different languages. I think you don't need to avoid monetizing the service. Instead, if the stuff is good and easy to use, your contribution by removing heavy flash cards gives users more convenience. In real life, people help each other as friends. But since we can not help each others as strangers, so we exchange money. When you have money and you really like your service and users, you will put the money into making your service better because now you have resources to hire more people to deal with something that volunteers, users community won't/can't. And you still can have money for yourself to live a good life, and I think they won't mind that and are happy that because you deserve it! Also, you somewhat underestimate the chance that your learning tool is really better than flashcards and help students learn better. Think about this: there are probably around order of 100 millions kids in the world that need to learn English in schools. Maybe 5 millions of them really want to learn English well for their future careers and they will invest their time and money to learn it well. While your contribution to make 5 millions people have a better time in life. They may just buy a set of flash card for $10 for a semesters and throw them away, meanwhile your service is fun and they learn much faster and better. So in order that your server can handle the traffic, you can just price it as the flash cards and see how people take it. Begin of edit: Your product is not Microsoft Windows. You don't force people to use it. You don't bully your competitors. So you should not feel guilty of taking money for your achievement. If you really want someone else to take care of it. Make it open source and see how the world react to it. End of edit.