George Zimmerman -- FIGHT IS OFF Again ... After Trayvon Martin Family Refuses Donation

George Zimmerman will not be bare-knuckle brawling ... TMZ has learned the celebrity boxing match has been canceled again after Trayvon Martin's family refused to accept any money from the fight's promoter.

As we reported ... FilmOn.com CEO Alki David wanted Zimmerman to fight multiple high profile opponents in a fight-club style match ... and said he would donate all profits to the foundation created by Trayvon Martin's family.

But late today the foundation told TMZ it would NOT take any money from the fight, saying it "stands boldly against any act of violence" and would reject David's donations.

When we called David for comment he decided to pull the plug altogether, saying ... "I respect the wishes of the family and in light of this we are canceling the event."

The original bout -- planned with DMX -- was axed when the first promoter got 2nd thoughts ... and death threats.