First, Riot Games (well a subsidiary) sued Valve for filing a trademark claim (necessary to get the franchise legally going). Riot Games sold the DotA-Allstars, LLC (
Limited liability company - Wikipedia) to Blizzard (lol) and Blizzard continued the lawsuit. And of course, the Chinese being their communist selves, uCool released a game with DotA characters and declared DotA was a open source collective work (with emphasis on collective

) and that it could not be copyrighted.
The story can be read here:
Dota 2 - Wikipedia
The fact is they fought for a name.
TL/DR: Valve - Blizzard was regarding a trademark that was filled shadily about the
name "DOTA"; Ucool case was regarding copyrights regarding the
game DOTA. The decisions and debate don't follow the same reasoning as trademarks are not akin to copyrights.
I hate being the obnoxious law dude that no one listens but i think you will listen me deepstrasz as you atleast listen to what others have to say on a regular basis.
Blizzard/RIOT and Valve case was in respect of a trademark, in this case a name: "DOTA". A trademark is not akin to our more convenient copyrights, this meaning that a trademark is NOT a copyright regarding a name or denomination. A trademark is just a piece of information (ie. a slogan, a name, an icon) that helps consumers identify products, granting the claimer of it (ie. the company that obtains the registration) some rights to exploit such information on the commerce while baring anyother doing so. One could say that the keyword for understanding trademarks is "commercialize". Copyrights, for most countries, born with the creation of the work (ie. you create a game that you called Dota) and belong to the material author barring some exceptions. Now notice that trademarks recquire a more formal procedure to actually born (ie. in my country i need to register them). The only thing in common these two have is the subject (intellectual property). So in conclusion: trademark is a type of IP different from copyrights.
Can i register a trademark regarding a name? Sure (ie. McDonalds), as the limits are not related of how creative such name is but are related to the integrity of the market information, so consumers are not scammed in what they buy everyday. Plain names can't be copyrighted at all, as there is little creative span here on creating a name. Since Copyrights born the instant one creates a work, notice how fucked could be that somebody could have a monopoly over a short denomination or ideas and concepts. One thing is to name one of your original characters "Rexxar" (you will not be sued for that, atleast for copyright claims, maybe you are in for trouble if you try to confuse consumers) but other thing is to borrow the entire character from the Warcraft universe into your product (ie. your custom game, your novels) without permission. Let's say i make a game about zombies and one of the caracters is a barbarian like beastmaster that lives in Durotar called Rexxar. If i do this, the cease and desist letter will come in a week. And i would be a lazy idiot too.
Now let's think critically.
According to that Wikipedia entry, Rob Pardo said this: "the
Dota name belonged to the mod's community". What we could say to this dude Pardo? Isn't he freaking wrong?
Now let's think critically again. The EULA mandates (i bet since its first version) that custom games can't be exploited commercially. If i want to register a trademark regarding the name of my custom game, understanding that a trademark is most often be used to commercialize something, am i in for some trouble or not? What if i register it in my country but i don't commercialize anything?
Ucool case is much more interesting for us. Ucool case i read years ago and i don't feel like reading it again, but bear with me. Ucool case is related to copyright law and the good news is that the judge understood that the implicated copyrights are regarding the game itself (the DOTA game, the audiovisual display we get on the screen when we play it, NOT the name). Regarding the game, the judge attributed joint ownership to Eul, Icefrog (Abdul Ismail) and, if i recall correctly, other dude called Jynzo or something. This is good news for everyone: copyright belongs to creators. Didn't i said this million times? The Judge didn't said Blizzard or Valve is the owner. You are all clear guys. This doesn't show on the Wikipedia also.
The Ucool thesis was based on random posts of Eul and Jynzo that could "implied" that they forfeited their copyrights on the game to the public domain. The judge dismissed this mostly because Icefrog didn't post anything about this topic. Remeber that DOTA is a joint creation so, naturally, if a waving of rights is to be made, it should be maded jointly. Isn't this pure common sense guys?
Thus the judge easily dismissed the Ucool theory that the DOTA (the game guys, don't focus on the name) belongs to the community. As a last resort, Ucool even said that all this was fucked up as Icefrog breached the contract with Blizzard (the EULA) by exploiting DOTA commercially (something very interesting as i mentioned above). Of course only Blizzard is the one entitled to promove such claims so this was naturally dismissed.
EDIT: Ucool case was about copyright but it wasn't the case that acknowledge potential copyright ownership over a map like Dota (and the joint works discussion). This was Blizzard v. Lilith. Enjoy.