Endless Online is described as 'free-to-play 2D MMORPG with cute, old-school anime graphics. The usual character development, monster hunting, trading, and customization are available here' and is a Role-playing Game in the Games category. There are six games similar to Endless Online for a variety of platforms, including Windows, Linux, Mac, BSD and PortableApps.com. Most alternatives are Role-playing , MMORPG Games and Adventure Games. The best alternative is The Mana World, which is both free and Open Source. Other Endless Online like games are Stendhal (Free, Open Source), Angels Online (Free), Tree of Savior (Freemium) and Key To Heaven (Free).
The Mana World (TMW) is a serious effort to create an innovative free and open source MMORPG. TMW uses 2D graphics and aims to create a large and diverse interactive world. It is licensed under the GPL, making sure this game can't ever run away from you.
By yourself or with friends, your goal is to fight and explore on the mysterious islands. Become stronger, equip better items, craft a raft and sail parts of the oceans to find more hidden treasure, secrets, and bosses.
NosTale is a free-to-play 2D casual MMORPG which takes gamers through seventy exciting levels of the wonderful world of East Mile. Gamers can choose from one of three character classes, each with unique powers and features.