It’s not an easy-to-answer question!
Ars Technica writes about how Valve, developers of Dota 2, has sued Lilith Games and uCool for two mobile MOBA games – namely, Dota Legends and Heroes Change, respectively. uCool refuses to just swallow a pill, and they decided to strike back: they don’t think Valve owns the source material that was used to make Dota!
uCool claims based on a 2004 forum post that the original creator of the mod for Warcraft 3 (Dota started out its life as such!), Eul, has made the mod available for free, which means the lore and the characters are fair game to use. A court order () says that Eul’s forum post, regarding its „abandonment,” is vague, and thus, a jury should be deciding about whether Valve owns the property or not. Valve had previously come to an agreement with Blizzard back in 2012.
This is going to be an interesting decision by the jury…