Copyright restrictions are constraining the user-generated content revolution, Stanford law professor Lawrence Lessig has argued in an opening keynote at the LinuxWorld conference in San Francisco.

Lessig is a founder of the Stanford Center for Internet and Society, and co-creator of the Creative Commons licence.

He is a known proponent of reduced legal restrictions on copyright, trademarks and the radio frequency spectrum, particularly in technology applications.

Copyright restrictions are designed for a world in which small elite firms create media for the masses, but such a structure is an historical anomaly, according to Lessig.

"Never before had a production been as concentrated and as professionalised, " he said.

Lessig described the original situation as a 'read-write' structure, where individuals are able to both create and consume media. The copyright restrictions of the 20th century, however, form the equivalent of a 'read only' culture.

Examples of the 'read-write' culture are commonly found on services like YouTube, where consumers mix and match existing media to create new media and express opinions, exercise criticism or propagate views.

"The law as currently architected smothers this read-write creativity," said Lessig.

Although artists have a right to be compensated for their work, Lessig believes that society needs to strike a balance between preventing piracy and encouraging individuals to "build and spread our culture".

Children today are already practicing the read-write culture, Lessig pointed out. "We can't kill this, only criminalise it. We can't force them to become the same couch potatoes that we are. We can only make them pirates," he said.

Lessig concluded that we are living in an "age of prohibition" and called on open source developers to create technologies that challenge the notions around copyright.

He argued that developers demonstrated an ability to challenge conventions before when they defeated the Windows monopoly.

Several artists, for instance, have released music under Lessig's Creative Commons licence, encouraging others to mix and use it to create new culture forms.

He also referred to services such the Gnash free Flash initiative and the Ogg Vorbis open source audio encoding format. 

Open culture is not just an idealistic, left-wing project, Lessig stressed. It will also foster economic growth.

"Only you can teach that to those outside your world," Lessig told delegates at LinuxWorld. "Elsewhere too few of us get it."