According to this site, this is the 3rd draft by Lucas, which was written after Leigh Brackett died and before Kasdan was hired. I found the actual Brackett draft, and it does not match this. Could it really be the Lucas 3rd draft as it says? If so, it would be something to discuss as it's never been posted as far as I know. http://www.oocities.org/eh_field7/movies/scripts.html If this is not it, it would be great if someone out there would post the Lucas draft online. Update: This appears to be a mislabeled script. They even thought it might be another Brackett draft, but that was wrong. It's actually the 4th draft by Kasdan. The page was confused. http://www.starwars-union.de/diefilme/episode4/30jahrekds/THE EMPIRE STRIKES BACK - Fourth Draft - Shooting Script - Oktober 1978.pdf
Yeah, Kasdan came on the team in April '78, so by October he wwould have been well entrenched in the scripting process. Thanks for posting the link, though, it's a fun read.
Just a minor correction, Lucas didn't write the third draft. He wrote the second draft (and revised second), in April 1978. Kasdan wrote the third draft in August .