The PDF is available for free and there is an ‘open source’ Word version where he will capture user suggestions.
In the digital world the marginal cost of producing an extra copy is zero – which is what underpins my belief in the trend towards free and the need for new business models. McAfee explains it like this in his textbook:
Economics studies the allocation of scarce resources among people – examining what goods and services wind up in the hands of which people. Why scarce resources? Absent scarcity, there is no significant allocation issue.