Fanworks are allowed on tapas, but not really encouraged and unlikely to be promoted. You also can't make profit of of them. In the worst case scenario you'll get a cease and desist and have to take it down or I bet the tapas team might take it down themselves, but I haven't really seen that happen personally.
However, if there's no mention of concepts of the original story (that not only includes characters, but locations, unique creatures and concepts as well) then I'm pretty sure it's fine to monetize. There's plenty of examples of popular works that started as fanfiction after all!