Does that mean that RadarBox users will be able to supply data to the PP MLAT programme?
Unlikely.
MLat doesn't do its calculations based on the socket output (since there's no useful information output in the socket data for non-positional aircraft by either RadarBox or SBS).
So the answer is no, while socket output compatibility is desirable for lots of add-ons, on its own it won't facilitate MLat.
Having said that, I'd be surprised in AirNav aren't working on MLat solutions :-)