When he coded software back in 1973, the idea was "write once, run everywhere," he said. In 2005, that mantra might seem far-fetched at a time when thousands of Microsoft sales professionals license loads of software to consumers and businesses.

But Moglen said the Free Software Foundation and the Software Freedom Law Center he chairs are trying to return software to its glory days of shared development.

"We are responding to a lengthy, but temporary period during which software was a proprietary, closed science…" Moglen told the audience. "The consequences of that process produced bad software at high prices. We are reversing that situation. What we do is help people think well and share."

Moglen, who sharply disagrees with software patents because they hinder free use models, advocates the two existing models of free software provisions. One is for permissive use, which allows anyone to use, modify and make a piece of software into any product. BSD licensing is an example of this model.

The other model, which includes the GNU General Public License (GPL) maintained by the Free Software Foundation, permits users to use, modify and make applications with code, with the understanding that it may not be used in proprietary products.