You can earn this TBD friends badge meta badge badge at the TBD assembly by proving (for instance by taking a selfie or by bringing your friends with their badges to the TBD assembly) that you were, at some point in time (i.e. simultaneously), present in the same location as:

• a version 1.0 TBD friends badge (black)
• a version 1.5 TBD friends badge (blue)
• a version 2.0 TBD friends badge (purple)
• a version 2.5 TBD friends badge (red) and
• a 39C3 friends badge