So this is not too hard, anyone could do it if you don't already have it.
Or if you have too many.
No real hassle, it works for steam and it's not warez and can't be a virus.
Go to:
steamcommunity.com/id/dota2bot
Follow the instructions there and you will have your Dota2 in no time.
If you somehow don't understand the instructions.
Code:
1. Add the bot as a friend, it takes a second (Unless it's offline) 2. Open a chatwindow to it and say this exact phrase without the quotation marks - "give dota"
And if you didn't manage to mess that one up you should now have dota 2. 3. Enjoy.
This also works as a trashbin for all your unwanted dota2 copies, just gift them to the bot and get a clean steam-inventory.
Have fun.