It's not his first radio software. Almost a decade ago he wrote the rtl-sdr ADS-B software dump1090 https://github.com/antirez/dump1090 . It was much easier to set up and use than prior GNU Radio 3.6 gr-airmodes (c++/python) + Virtual Radar (java) options. It went on to be forked and improved upon and it is now the community standard.