From LinuxTag Public Wiki
eTickets are electronic 4-day passes for visiting LinuxTag. LinuxTag will provide each participating project a bunch of eTickets, which should be spread among the project's community.
The tickets will be distributed in May.
Important: Because we encountered some problems last year, we urge you to activate your eTicket account immediately after reception of the mail from the system. You must log in within 48 hours to activate or the eTickets will are forfeited. Once you have logged in, all eTickets will remain valid until the fair.