What's the best way of broadcasting nmea (or other data) to the network?
Can gpsd do this, or do you use netcat/socat?
What do you mean by broadcast: making your receiver accessible to any interested client on the network that chooses to connect, or actually sending datagrams to the network broadcast address?
The "-G" flag will cause gpsd to bind to INADDR_ANY instead of localhost, thus allowing other devices to connect (subject to packet filters); each client is responsible for connecting when it needs GPS data. There is no flag in GPSD that would cause it to fling udp datagrams, containing gpsd ndjson reports, to the broadcast address. You could do the latter with a screenful of python (connect to gpsd, turn on gpsd, read a line from gpsd, send a datagram to the network, repeat), and maybe with netcat too.
If you're broadcasting GPS data over UDP, would it be a problem for you if a rogue device started spraying bogus data?