Dota began life as Defense of the Ancients, a mod for WarCraft III that became as popular as the game that hosted it (arguably moreso). As a mod, its history of creation is somewhat muddy, as it was cultivated by multiple people over the years, included community feedback, and was eventually the center of a court case between Valve (which bought the rights to the mod from then-caretaker Abdul "IceFrog" Ismail) and Blizzard (the company who owned the game Dota was created within), eventually settled out of court. At that point, it seemed clear the game belonged to Valve (with a little wiggle room for Blizzard to associate the name with its games). Now, a federal court case once again asks: Who owns Dota?
As Ars Technica reports, the case revolves around Dota Legends and Heroes Charge, two mobile games allegedly infringing on Valve's Dota copyright. The first argument has to do with whether Dota is a collective work (a collection of separate works that have been assembled). Heroes Charge developer uCool argued in court this was the case, since it "took the most popular Dota heroes and arranged them into a new game," (if this were the case, the same could then be said of Heroes Charge). Judge Charles Breyer dismissed this argument. "By that logic," said Breyer, "Star Wars: The Force Awakens would be a collective work because it arranged the most popular Star Wars heroes, settings, and one-liners into a new movie."
The second argument involves Blizzard's End-User License Agreement for WarCraft III. Though it doesn't provide Blizzard with the rights to any of the mods created in WarCraft III, it does states players could not use anything they made with the game's game creation tools for commercial gain. According to Breyer, Ismail's eventual sale of Dota to Valve "seems as commercial as uses go."
The third argument could have some repercussions, if it goes uCool's way. On September 23, 2004, Dota's caretaker at the time, Kyle "Eul" Sommer, posted on the WarCraft forum Warcenter that "from this point forward, Dota is now open source. Whoever wishes to release a version of Dota may without my consent, I just ask for a nod in the credits to your map." Though Breyer asserts this could mean anyone is able to make a version of Dota to sell, he mentions that its vagueness leaves it open to interpretation. For one, that forum post could refer only to other mods, and not commercial products. Second, as a post on a small (albeit public) forum, the post may have been meant only for Sommer's fellow forum posters.
Breyer has denied uCool summary judgement, which means the case may move on to face a jury, which will have to decide whether Valve has a legitimate claim on Dota. If uCool wins the case, that could potentially open the door for all kinds of Dota clones to enter the market.
I'm no lawyer, but this case seems like a real mess. If the EULA argument holds, then neither Valve nor uCool have a right to create commercial products based on Dota. But if the open-source argument holds, they both do. Valve later hired Sommer and bought out his rights to the game, making any current clarifications from him about his forum post questionable. Although the question of Dota's ownership has mostly settled on Valve in the public eye, there doesn't seem to be a concrete path for Valve alone to hold the copyright, though a Jury could ultimately decide as much. Considering how murky the entire history behind Dota's ownership is, I don't envy the jury.