[wdaher]

Yep, that's correct--as far as I know, the original source code isn't actually available anywhere.

Three independent groups, at Berkeley, MIT, and Purdue disassembled the .o and poked at its contents, slowly figuring it out.

Mark Eichin's timeline (http://web.mit.edu/user/e/i/eichin/www/virus/chronology.html) is a fun read, written from the MIT viewpoint, that chronicles how the Unix nerd community basically sprung up to dissect and deal with the worm, and contains a section on their attempts to disassemble the worm.