Update to Steam Beta. Steam > Settings > Beta Participation
Go to you Steam/Public/steamui_english to verify
"SteamUI_JoinDialog_SharedLicense_Title" "Shared game library"
"SteamUI_JoinDialog_SharedLicenseLocked_OwnerText" "Just so you know, your games are currently in use by %borrower%. Playing now will send %borrower% a notice that it's time to quit."
"SteamUI_JoinDialog_SharedLicenseLocked_BorrowerText" "This shared game is currently unavailable. Please try again later or buy this game for your own library."
Found it on Reddit. Don't know if it is fake or legit.