I like the weather option - on a number of occasions I've called up London Information to get weather information on airfields, particularly when on a flight the "long way" across the English Channel. Having some OGN-R stations along the south coast with some large yagi antennas pointing out over the sea would be great!
I don't see anyone giving away anything to anyone else. As far as I understand it, Sky Demon will take weather inputs on the GDL90 messages. There are two things Sky Demon could do - add proprietary messages to the Flarm format in conjunction with PilotAware for the weather messages, or add proprietary bearingless traffic messages to GDL90 also in conjunction with PilotAware. This doesn't give anything to the SE2 owners. SE2 can pick up the UAT 978 transmissions which can also supply weather, and which are then communicated to Sky Demon over GDL90.
The purpose of the original message I believe was to gauge the response for Lee to code the PAW to transmit the received TAFs and METARs into GDL90 so if you select that, Sky Demon will automatically pick these up.
Back in the day when we trialled UAT 978 reception on PilotAware, the FIS-B weather data was able to be sent from the PilotAware to Sky Demon over GDL90.