A community manager confirmed that Valve is porting the game
Dota 2, Valve's own take on the famous Dota mode for Warcraft 3, will be arriving on Steam for Linux soon, or at least this is what a community moderator says on the official Valve GitHub channel.Valve has a way of not confirming or denying something up until it's actually launched. It's unclear why they are dancing around this issue, but it was unclear whether Dota 2 would actually make it to the Linux platform.
One of the community moderators on Valve's GitHub channel took it upon himself to inform the fans, after reassuring everyone that he is not working for Valve.
“You don't need to vote for them porting Dota2 because they already are porting it. They are working on it. They need to get the simpler games ported over first or else Dota2 won't be playable for considerably longer,” stated the moderator.
It seems that Dota 2 is using a modified Source engine and it's harder to port than the rest of the other titles.
More details about Dota 2 on Linux will be posted when the official announcement arrives.