It probably does, but that hasn't stopped a US federal court from taking a closer look at the question. Two mobile developers, Lilith Games and uCool, have tried to make clones of Dota 2 for smartphones and been sued by Valve as a result.
Their games, Dota Legends and Heroes Charge respectively, are slimmed down MOBAs that are popular in China. As Ars Technica reported, in response to Valve's copyright claim against them, uCool has argued that the company doesn't actually own the source material that Dota is based on, make its claim illegitimate.
Dota started originally as a mod for Warcraft 3, making the question of who owns the rights a complicated one. Citing a forum post from 2004, uCool argued that because the original creator of the mod that would eventually evolve into Dota, Eul, had "released" it to the public, the lore and characters are fair game for anyone to use.
"I wish I could give you a last map that's playable, but I can't. Instead, from this point forward DOTA is now open source," Eul wrote back in 2004. "Whoever wishes to release a version of DOTA may without my consent, I just ask for a nod in the credits to your map."
uCool's Heroes Charge uses characters straight from Dota 2.
In a court order this week denying uCool's motion for a summary dismissal of Valve's suet, Judge Charles Breyer decided that the question of "abandonment," whether Eul had relinquished his rights to the mod as a result of his forum post, would be reasonable for a jury to pursue given the vagueness of Eul's statement and the context surrounding it. As a result, the case will move forward.
But Breyer also raised some other interesting issues, like whether Blizzard's own EULA (End User Licence Agreement) prohibited Eul from having any rights to Dota in the first place, due to a clause that restricts mods from being distributed for commercial purposes. Valve and Blizzard came to an agreement Dota back in 2012, three years after the former had acquired the intellectual property rights to the content of the mod, but Breyer's reasoning in his recent court order casts some doubt on whether the company was in a position to purchase those rights to begin with,
"The EULAs did, however, make clear that players could not 'use or allow third parties to use the [World Editor or mods] created thereby for commercial purposes including, but not limited to, distribution of [mods] on a stand-alone basis or packaged with other software or hardware through any and all distribution channels, including, but not limited to, retail sales and on-line electronic distribution without the express written consent of Blizzard.' Id. ¶ 3.C.iii. Mods were for play, not pay."
From here, the case will go before a jury to decide the question of who owns the rights to Dota and whether uCool and Lilith Games are in violation of those rights with their respective mobile clones.