I don't know if they have any grounds to make this lawsuit, but really, Valve should not be using the name Dota 2. That's just dumb.
The only company that should be using the term Dota on a product is Blizzard, and even then....I don't really think they should.
But Valve? No way. I love Valve, but if they want to make a Dota clone, they really don't have the right to it. Even if Icefrog is working with them. He didn't invent Dota either.
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The batman villians all seem to be one big joke that batman refuses to laugh at - SantaRPG