Kurso de Esperanto is described as 'multimedia computer program for teaching yourself Esperanto. Here are several of its features:' and is an app in the Education & Reference category. There are three alternatives to Kurso de Esperanto for Online / Web-based. The best alternative is lernu!, which is free. Other great apps like Kurso de Esperanto are I Kinda Like Languages (Free) and Kurso de Esperanto (webapp) (Free, Open Source).
I kinda like languages is website with free online introductory and basic language courses of different languages of the world. The courses are made by volunteers and the website is targeted for people who want to learn many languages.