Blizzard is taking steps to legally contest Valve’s trademarking of the ‘Dota’ name, claiming that the title is “firmly associated in the mind of consumers with Blizzard”. Valve is planning to release
The history of Dota (which, although almost always referred to be acronym now, originally stood for ‘Defence of the Ancients’) begins with a custom-made map for Blizzard’s Warcraft III. Two of the three main people responsible for that map were subsequently hired by Valve (with the third now at Riot Games, makers of League of Legends).
One of the two at Valve, a chap known as ‘IceFrog’ is the lead designer of Valve’s Dota 2. Valve took steps to trademark the name ‘Dota’ (though not, it seems ‘Defence of the Ancients’).
It’s difficult to speculate where the case will go from here. Blizzard contends that the ‘a’ in Dota stands for ‘Ancients’, who are associated with the Blizzard property Warcraft III. However, Dota was created and nurtured by the community, and two of the major players in its creation now work for Valve.
The hypothetical trial schedule (which you can read through the source link, below) runs well into 2013, so unless a settlement is reached we could be hearing about this for quite some time.