KerberosSDR and later KrakenSDR are precisely this, and the guy behind it got a spanking after putting up a passive radar implementation that actually works ok publicly on GitHub sometime in the pre-AI era. Supposedly it was considered an ITAR issue, but the similar MLAT capability instead of phase coherent sensing like you get with a Kraken is basically deployed everywhere today (all of the ADS-B nodes that feel FlightAware, FlightRadar, etc.) It's certainly not novel and not in the way TFA wants to paint it.