Well, this 5V is a pass through from the power input module. There is nothing limiting the current other than the ratings of one steering diode PMEG2020EPK, the board traces and connectors. The power module is not specified, but typically 2-3 amps. The connectors are 1 amp per contact. The Diode is 1A. Having said all this, I would not plan on drawing more than something like 100mA from the 5V supply provided from the FMU. If you need more than that, it would be reccommended to use a separate BEC (external regulator).
