Stallman was in Australia to speak at the World Computer Congress when he showed up at the meeting with a placard that read: "Don't get caught in software patent thickets."
The meeting was a presentation by European Patent Officer Ralf Abbing, who was speaking about the "big issues in IP in relation to computing technology," reported ITNews.
Stallman is a strong proponent of getting rid of software patents entirely. He said he supports the developer-led petition to abolish software patents in Australia.
The European Patent Office was lobbying for software patents in Australia.
"You can be sure that if Australia allows software patents, almost all the patents will belong to foreigners and will give them the opportunity to sue Australians.
"There's no problem that requires a solution with anything like software patents. Without software patents ... neither of us would get sued by the various patent troll companies whose sole business is collecting patents so that they could go threaten people," Stallman said.