Police arrested 46 people in the capital Harare on February 19 as they watched videos of protests in the North Africa states and discussed possible demonstrations in Zimbabwe, where Mugabe, 87, has held power for 31 years.
Defense lawyer Alec Muchadehama said state prosecutors had agreed to free a majority of the accused activists, who faced treason charges and possible execution if convicted.
“Out of the 46 who were in custody, 38 have been released completely after the state agreed with us that they had no case to answer,” he told reporters.
Muchadehama said the remaining eight — including Munyaradzi Gwisai who heads a small but radical pressure group called the International Socialist Organization — would be back in court for a remand hearing session on March 21.
They had all pleaded not guilty.
Defense lawyers say the accused were engaged in an academic debate on African politics when the police pounced on them. International human rights groups had appealed for their release.
Those arrested included trade unionists, student leaders and Gwisai, who is accused of convening the meeting.
Critics say Mugabe has used brutal policing and vote rigging to keep his grip on power despite an economic crisis in the past decade that many blame on his mismanagement.
Mugabe was forced into a power-sharing government with rival Prime Minister Morgan Tsvangirai’s Movement for Democratic Change (MDC) about two years ago, and is pressing for fresh elections this year.
Many say this would favor Mugabe’s ZANU-PF party if no major political reforms are put in place, including a new constitution and improved voter registration.
Tsvangirai has said his MDC would boycott any general election called before these reforms.
Internet campaigns calling for Egyptian-style street protests against Mugabe’s rule have failed to prompt any mass gatherings in a state where police have crushed previous attempts at demonstrations.
Editing by Jon Herskovitz