No GNU Radio needed. I can compile a windows binary if needed. Just be aware that the program runs from the command line, there's no GUI. It's not too hard to get going.
On the squarial, as Captain Jack says the hackrf won't transmit on the frequencies needed. We're using the intermediate frequencies (IF) as would have been output by the squarial, feeding it straight into the receiver (with a DC block to protect the hackrf from the receiver's LNB power). I've a frequency list here:
BSB Frequency List
If you have an FM modulator that can transmit at 12GHz then it might be possible to feed it the baseband from an fl2k adaptor. This would be a fun experiment!