If you can kick it over the pistons either aren't seized (anymore?) or something major has broken. Sounds to me like it is working more or less like it should.
With the trans in neutral you should be able to kick it over with the kick starter, clutch pulled or not. I don't know if that model had a clutch interlock or not but it may, that "probably" would only either electrically lock out the electric starter and/or disable the ignition.
At this point I would pull the plugs, and shoot some light oil in the cylinders and work it some more.
Time for a battery and see if it has any life in it.
Also, I don't remember if it's been mentioned on this thread but don't forget the tires. Even if the tires on it look good, if they are vintage to the bike they are dangerous and need to be replaced. When motorcycle tires get old they get harder than Chinese algebra and they will put you on the ground.
A buddy of mine resurrected a late '80s Goldwing a few year ago, I gave him the same advice. He didn't listen. I miss him.
He retired and I haven't seen him since but he did have the bike slide out from under him with the old tires.