I would say that the 28A is the rated full load current. So you will need a drive capable of driving 28A @ 24VDC.
Not really sure about that . . . 28A at 24V is 672W . . . perhaps that's output power, after subtracting efficiency?
Some motors are rated by no-load, while others are rated at stall. 90% of the time they are rated at no-load. You can't really know without using the motor or seeing torque/current curves in a datasheet.
It appears to come from China, and no datasheet available, at least with google . . .