I just started thinking about this... Was it Calus or Dominus Ghaul they were trying to contact? Calus; he comes to our system to celebrate our victory over the Red Legion. Almost as if hes trying to make a peace treaty. Get us to join his side in the Cabal civil war. Ghaul: comes to our system personally to take the light to overthrow Calus. It actually makes more sense for them to be trying to contact the Red Legion in that mission, because the Cabal are in civil war between their Emporer (who has become lazy and forgotten the warlike ways of the Cabal and instead pursues luxury) and Dominus Ghaul and the Consul leading the rebellion at the head of the Red Legion. So it makes sense that the Skyburners would be loyal to the Red Legion side and Ghaul sent them here to claim the Light or scout out our solar system for the Red Legion. Also, they were likely given the command to stop Oryx from destroying the Light, hence why they were ordered to crash into the Dreadnaught. They were expendable to the Red Legion... So my money is Ghaul. Yes the Skyburners were loyal to the Red Legion. Also, there is the fact that there is a weapon in Destiny 2 called "Skyburners Oath".