A paid version with more features seems like a safe way to go; moving into the freemium model, somewhat. If not enough people buy it, you can always fold the fe

A paid version with more features seems like a safe way to go; moving into the freemium model, somewhat. If not enough people buy it, you can always fold the features into the free version (though be careful about that; people who do buy a paid version may feel ripped off if the free version has all the same features). Other than that, you can always put a donate buttons somewhere, though I'm not sure how effective that would be.