It has just been announced and made a reality: Counter-Strike: Global Offensive is now fully Free-to-play with the introduction of a New Battle Royale Mode, the Danger Zone, a very welcomed and exciting move coming from Valve. Now anyone can give CS a proper Go and enjoy one of the most popular multiplayer shooters of all time.

CS:GO is now FREE TO PLAY. So there’s never been a better time to bring in your friends.
All players who played CS:GO before today’s update will receive a commemorative Loyalty Badge they can display on their profile. You were there from the beginning, so show it off! Additionally, all existing CS:GO players have had their accounts upgraded to Prime Status.
As before, Prime Status matches you with other Prime Status players. Additionally, your Prime Status will give you access to the new Souvenir MP5-SD | Lab Rats (available by earning XP while playing Danger Zone matches) and the all new Danger Zone Case. (Valve)

https://store.steampowered.com/app/730/CounterStrike_Global_Offensive/
http://blog.counter-strike.net/index.php/2018/12/21519/