Former Cosatu general secretary Zwelinzima Vavi and EFF leader Julius Malema are plotting to overthr.
"The government is caring only about themselves. They don't care about you," Malema -- who is starting his own party, the Economic Freedom Fighters (EFF) -- told a large crowd.
Malema, EFF spokesman Floyd Shivambu and businessman Kenny Kunene had attended an urgent application brought by lawyer Dali Mpofu for the State to fund the legal representation for the victims of the Marikana shootings.
Police shot dead 34 striking Lonmin miners and wounded 78 in Marikana, North West, on August 16 while trying to disperse them. The inquiry is into the events surrounding the shooting, and the deaths of 10 people in strike-related violence the previous week.
A large group of miners and their families had gathered in front of the court since Thursday morning, and they sang and danced in Church Square. Some held up placards reading: "Don't let the police get away with murder".
While addressing them, Malema said Zuma's "murderous regime" killed the miners.
"They pay only the lawyers of murderers. Those who have killed people are getting money."
Malema called national police commissioner Riah Phiyega "a useless person", and said that was why she had been unable to answer any questions during the inquiry.
Referring to Zuma and Police Minister Nathi Mthethwa he said: "They must know they will go down in history as murderers".
He said the Farlam Commission was a serious matter, as people who were found to have been in the wrong could go to jail. He told the cheering crowd they were constitutionally entitled to legal representation.
"They are not doing you a favour."
He said the government had already decided the people were wrong and believed they were criminals.
"That commission, I personally don't trust it," Malema said, adding he believed it had a predetermined outcome.
"We will be together forever. We have always been with you," he said, urging them to fight for a monthly wage of R12,500. We must do everything in our power to force them to give you that R12,500."
The demand for a R12,500 monthly wage was what motivated the miners' strike in August.
During the court proceedings, Mpofu told Judge Joseph Raulinga it was unlikely the commission would finish its work by the extended deadline of October 31.
Mpofu represents the miners wounded and arrested during the shooting on August 16, at the commission's hearings.
He said the legal team had not received any funding for June to October, and suggested interim relief, so as not to interfere with the commission, which is due to resume on Monday.
The case continues.