The 41-year-old Assange violated a condition to report to a police station daily when he sought refuge at the Ecuadorean Embassy in London, where he has been holed up since June 19 to avoid extradition to Sweden to face questioning over sex crimes allegations.
The WikiLeaks founder and his supporters claim that the Swedish sex case is part of a Washington-orchestrated plot to make him stand trial in the United States over his work with WikiLeaks, which has published thousands of secret U.S. diplomatic cables and other documents. Both Sweden and the U.S. reject that claim.
Former BBC journalist Vaughan Smith, who hosted Assange at his country house for more than a year as the WikiLeaks founder fought extradition, was among the nine supporters who had argued that they should not be punished for trying to "serve the public interest" in the case.
But Chief Magistrate Howard Riddle on Monday ordered them to pay 93,500 pounds ($150,000) by Nov. 6, saying that while he accepted the supporters had acted in good faith, they had failed in their "basic duty" to ensure Assange surrendered.
"They must have understood the risk and the concerns of the courts," he said in his ruling, ordering each of the nine to pay part of 140,000 pounds ($224,300) originally pledged.
Still, the judge said he respected the supporters for acting against their own self- interest in refraining from urging Assange to surrender.
"They have acted on their beliefs and principles throughout," Riddle said. "In what is sometimes considered to be a selfish age, that is admirable."
The other backers of Assange include retired professor Tricia David, Nobel Prize-winning scientist John Sulston, journalist Philip Knightley, Lady Caroline Evans, friend Sarah Saunders, Joseph Farrell, Sarah Harrison and Tracy Worcester.
Talks between British and Ecuadorean officials to resolve the deadlock over Assange's fate have not been fruitful. British officials say Assange will be arrested if he steps outside the embassy.