Do i understand correctly that every gamer should buy a game activation key. This key is checked by the miner to get acces to the games?
isn't this service subscription based? it is on playkey.net
It is, but you still have to buy games (most of them, especially the new ones) that you want to play.
If i already have a game i can use my license, right?
It depends I guess. It seems that you can play games you bought on Steam. If you bought your games somewhere else, it COULD not work. Not sure.
It would be interesting to know the official statement from Playkey regarding the game licenses and how they will enforce this. Via a key or another way?
Gamers have to buy a game either on Steam/Uplay/Origin... or on Playkey store. Game verification processed via game key you enter in you Steam/Uplay/Origin account.
Playkey has connected with all makor publishers and integrated their game launchers.