[mherrmann]

Firstly, I hope for you that your project becomes popular enough so you can make money with it in theory.

When that happens, I would suggest going the way of Sublime Text: Unobtrusive, friendly reminders asking the user to purchase the software. From my own experience I know that it's difficult and extremely tedious to implement a copy protection scheme because it involves a whole lot of things you don't think of at first: how do you ensure that your license keys aren't posted on the internet? Does the customer need internet access to activate a key? What if the customer complains that the license key doesn't work? What about new versions of your software? Keep it simple.

[amorphid]

I paid for Sublime Text to make the annoying "buy me" message go away. I probably wouldn't have paid if it didn't nag me, and I never would have tried it if it weren't freemium.

[SvenAndersson]

Thanks! Yes, this is something I agree with fully, and one of the things I feel works great with Sublime.

edit: And while I might not have been it clear enough in my post, I'm not delusional thinking I might be sitting on a gold mine here. But I think it would be nice for people to show their appreciation if they also benefit from the app as well, but for it to work there needs to be as little friction as possible. And I don't know if/what such service exist, and if it is worth the hassle.