PB Blaster is a good place to start. Patience and some gentle heat to help the penetrant to flow into the joint might help. This drive shaft has the fine spline into the crankshaft, so it could be an adventure getting it out depending on how rusted the connection is. Try working the driveshaft back and forth and in a circular motion so any slight movement will open the joint up for the penetrant to enter. With enough working it around, it should eventually work free. Others may have more suggestions. You can always try the 50/50 acetone/ATF mixture if the PB Balster doesn’t cut it.
-Ben