He was fighting cancer.
Ownership shares are not like salary (imho): they're not just for past work, but also for future contributions.
Without specifics on to what extent exactly they were planning to dilute him, I am not prepared to condemn BillG. YMMV.
Jobs' actual cheating through a straightforward lie to Woz wrt how much they got paid for Atari's contract job they did is FAR worse than a planning conversation BillG had. IMHO. http://www.rotten.com/library/bio/hackers/steve-wozniak/