tnx
Oddly, I get
spctl -a /Users/Jeremy/Downloads/RemObjects\ Fire\ -\ 10.0.0.2419.dmg
/Users/Jeremy/Downloads/RemObjects Fire - 10.0.0.2419.dmg: rejected (the code is valid but does not seem to be an app)
but once it’s done, Fire does open it fine and restart. It doesn’t close the DMG, though it probably should.