Dota2 is up to play for free but only to those who are lucky enough to be selected by Dota2 team. Alternative method to play Dota2 is by buying the game via Steam for 30usd. Should be no problem for those with extra cash.
But for those who wants to get an invitation for playing Dota2 without spending money, you can try your luck by following my guide. The step by step tutorial is written fully in my eBook.
I am now playing Dota2 for free with my friends ^_^
Feel free to give me your steam id after you managed to get one after reading this guide.