This was previously available as a opt in beta, but is now available for everyone.
Previously playing a shared game locked down the entire library, now it just locks the one copy of the game.
This is by far the best thing ever for me. My 10 year old son is always hogging the damn thing and I never get to play. π Thank you valve for locking only the game. Iβm so freaking happy, you have no idea. I still donβt understand the cooldown part, but meh, I got what Iβve always dreamed of, and that is what I care about.