The front calipers were usable with a rebuild. The rear...well...
Someone had worn through the friction material, through the metal backing plate and had started MELTING the piston!
Luckily, there's a new Galfer rear rotor that came with the bike. I also ordered some new EBC pads all the way around.
I looked at rebuild kits for the calipers but, honestly, I could get good, used calipers for way less than a rebuild kit. All of that is here now.